1DRBD.CONF(5) Configuration Files DRBD.CONF(5)
2
6 drbd.conf - DRBD Configuration Files
7
9 DRBD implements block devices which replicate their data to all nodes
10 of a cluster. The actual data and associated metadata are usually
11 stored redundantly on "ordinary" block devices on each cluster node.
12 Replicated block devices are called /dev/drbdminor by default. They are
14 grouped into resources, with one or more devices per resource.
15 Replication among the devices in a resource takes place in
16 chronological order. With DRBD, we refer to the devices inside a
17 resource as volumes.
18 In DRBD 9, a resource can be replicated between two or more cluster
20 nodes. The connections between cluster nodes are point-to-point links,
21 and use TCP or a TCP-like protocol. All nodes must be directly
22 connected.
23 DRBD consists of low-level user-space components which interact with
25 the kernel and perform basic operations (drbdsetup, drbdmeta), a
26 high-level user-space component which understands and processes the
27 DRBD configuration and translates it into basic operations of the
28 low-level components (drbdadm), and a kernel component.
29 The default DRBD configuration consists of /etc/drbd.conf and of
31 additional files included from there, usually global_common.conf and
32 all *.res files inside /etc/drbd.d/. It has turned out to be useful to
33 define each resource in a separate *.res file.
34 The configuration files are designed so that each cluster node can
36 contain an identical copy of the entire cluster configuration. The host
37 name of each node determines which parts of the configuration apply
38 (uname -n). It is highly recommended to keep the cluster configuration
39 on all nodes in sync by manually copying it to all nodes, or by
40 automating the process with csync2 or a similar tool.
41
43 global {
44 usage-count yes;
45 udev-always-use-vnr;
46 }
47 resource r0 {
48 net {
49 cram-hmac-alg sha1;
50 shared-secret "FooFunFactory";
51 }
52 volume 0 {
53 device /dev/drbd1;
54 disk /dev/sda7;
55 meta-disk internal;
56 }
57 on alice {
58 node-id 0;
59 address 10.1.1.31:7000;
60 }
61 on bob {
62 node-id 1;
63 address 10.1.1.32:7000;
64 }
65 connection {
66 host alice port 7000;
67 host bob port 7000;
68 net {
69 protocol C;
70 }
71 }
72 }
73 This example defines a resource r0 which contains a single replicated
75 device with volume number 0. The resource is replicated among hosts
76 alice and bob, which have the IPv4 addresses 10.1.1.31 and 10.1.1.32
77 and the node identifiers 0 and 1, respectively. On both hosts, the
78 replicated device is called /dev/drbd1, and the actual data and
79 metadata are stored on the lower-level device /dev/sda7. The connection
80 between the hosts uses protocol C.
81 Please refer to the DRBD User's Guide[1] for more examples.
83
85 DRBD configuration files consist of sections, which contain other
86 sections and parameters depending on the section types. Each section
87 consists of one or more keywords, sometimes a section name, an opening
88 brace (“{”), the section's contents, and a closing brace (“}”).
89 Parameters inside a section consist of a keyword, followed by one or
90 more keywords or values, and a semicolon (“;”).
91 Some parameter values have a default scale which applies when a plain
93 number is specified (for example Kilo, or 1024 times the numeric
94 value). Such default scales can be overridden by using a suffix (for
95 example, M for Mega). The common suffixes K = 2^10 = 1024, M = 1024 K,
96 and G = 1024 M are supported.
97 Comments start with a hash sign (“#”) and extend to the end of the
99 line. In addition, any section can be prefixed with the keyword skip,
100 which causes the section and any sub-sections to be ignored.
101 Additional files can be included with the include file-pattern
103 statement (see glob(7) for the expressions supported in file-pattern).
104 Include statements are only allowed outside of sections.
105 The following sections are defined (indentation indicates in which
107 context):
108 common
110 [disk]
111 [handlers]
112 [net]
113 [options]
114 [startup]
115 global
116 [require-drbd-module-version-{eq,ne,gt,ge,lt,le}]
117 resource
118 connection
119 multiple path | 2 host
120 [net]
121 [volume]
122 [peer-device-options]
123 [peer-device-options]
124 connection-mesh
125 [net]
126 [disk]
127 floating
128 handlers
129 [net]
130 on
131 volume
132 disk
133 [disk]
134 options
135 stacked-on-top-of
136 startup
137 Sections in brackets affect other parts of the configuration: inside
139 the common section, they apply to all resources. A disk section inside
140 a resource or on section applies to all volumes of that resource, and a
141 net section inside a resource section applies to all connections of
142 that resource. This allows to avoid repeating identical options for
143 each resource, connection, or volume. Options can be overridden in a
144 more specific resource, connection, on, or volume section.
145 peer-device-options are resync-rate, c-plan-ahead, c-delay-target,
147 c-fill-target, c-max-rate and c-min-rate. Due to backward
148 comapatibility they can be specified in any disk options section as
149 well. They are inherited into all relevant connections. If they are
150 given on connection level they are inherited to all volumes on that
151 connection. A peer-device-options section is started with the disk
152 keyword.
153 Sections
155 common
156 This section can contain each a disk, handlers, net, options, and
158 startup section. All resources inherit the parameters in these
159 sections as their default values.
160 connection [name]
162 Define a connection between two hosts. This section must contain
164 two host parameters or multiple path sections. The optional name is
165 used to refer to the connection in the system log and in other
166 messages. If no name is specified, the peer's host name is used
167 instead.
168 path
170 Define a path between two hosts. This section must contain two host
172 parameters.
173 connection-mesh
175 Define a connection mesh between multiple hosts. This section must
177 contain a hosts parameter, which has the host names as arguments.
178 This section is a shortcut to define many connections which share
179 the same network options.
180 disk
182 Define parameters for a volume. All parameters in this section are
184 optional.
185 floating [address-family] addr:port
187 Like the on section, except that instead of the host name a network
189 address is used to determine if it matches a floating section.
190 The node-id parameter in this section is required. If the address
192 parameter is not provided, no connections to peers will be created
193 by default. The device, disk, and meta-disk parameters must be
194 defined in, or inherited by, this section.
195 global
197 Define some global parameters. All parameters in this section are
199 optional. Only one global section is allowed in the configuration.
200 require-drbd-module-version-{eq,ne,gt,ge,lt,le}
202 This statement contains one of the valid forms and a three digit
204 version number (e.g., require-drbd-module-version-eq 9.0.16;). If
205 the currently loaded DRBD kernel module does not match the
206 specification, parsing is aborted. Comparison operator names have
207 same semantic as in test(1).
208 handlers
210 Define handlers to be invoked when certain events occur. The kernel
212 passes the resource name in the first command-line argument and
213 sets the following environment variables depending on the event's
214 context:
215 · For events related to a particular device: the device's minor
217 number in DRBD_MINOR, the device's volume number in
218 DRBD_VOLUME.
219 · For events related to a particular device on a particular peer:
221 the connection endpoints in DRBD_MY_ADDRESS, DRBD_MY_AF,
222 DRBD_PEER_ADDRESS, and DRBD_PEER_AF; the device's local minor
223 number in DRBD_MINOR, and the device's volume number in
224 DRBD_VOLUME.
225 · For events related to a particular connection: the connection
227 endpoints in DRBD_MY_ADDRESS, DRBD_MY_AF, DRBD_PEER_ADDRESS,
228 and DRBD_PEER_AF; and, for each device defined for that
229 connection: the device's minor number in
230 DRBD_MINOR_volume-number.
231 · For events that identify a device, if a lower-level device is
233 attached, the lower-level device's device name is passed in
234 DRBD_BACKING_DEV (or DRBD_BACKING_DEV_volume-number).
235 All parameters in this section are optional. Only a single handler
237 can be defined for each event; if no handler is defined, nothing
238 will happen.
239 net
241 Define parameters for a connection. All parameters in this section
243 are optional.
244 on host-name [...]
246 Define the properties of a resource on a particular host or set of
248 hosts. Specifying more than one host name can make sense in a setup
249 with IP address failover, for example. The host-name argument must
250 match the Linux host name (uname -n).
251 Usually contains or inherits at least one volume section. The
253 node-id and address parameters must be defined in this section. The
254 device, disk, and meta-disk parameters must be defined in, or
255 inherited by, this section.
256 A normal configuration file contains two or more on sections for
258 each resource. Also see the floating section.
259 options
261 Define parameters for a resource. All parameters in this section
263 are optional.
264 resource name
266 Define a resource. Usually contains at least two on sections and at
268 least one connection section.
269 stacked-on-top-of resource
271 Used instead of an on section for configuring a stacked resource
273 with three to four nodes.
274 Starting with DRBD 9, stacking is deprecated. It is advised to use
276 resources which are replicated among more than two nodes instead.
277 startup
279 The parameters in this section determine the behavior of a resource
281 at startup time.
282 volume volume-number
284 Define a volume within a resource. The volume numbers in the
286 various volume sections of a resource define which devices on which
287 hosts form a replicated device.
288 Section connection Parameters
290 host name [address [address-family] address] [port port-number]
291 Defines an endpoint for a connection. Each host statement refers to
293 an on section in a resource. If a port number is defined, this
294 endpoint will use the specified port instead of the port defined in
295 the on section. Each connection section must contain exactly two
296 host parameters. Instead of two host parameters the connection may
297 contain multiple path sections.
298 Section path Parameters
300 host name [address [address-family] address] [port port-number]
301 Defines an endpoint for a connection. Each host statement refers to
303 an on section in a resource. If a port number is defined, this
304 endpoint will use the specified port instead of the port defined in
305 the on section. Each path section must contain exactly two host
306 parameters.
307 Section connection-mesh Parameters
309 hosts name...
310 Defines all nodes of a mesh. Each name refers to an on section in a
312 resource. The port that is defined in the on section will be used.
313 Section disk Parameters
315 al-extents extents
316 DRBD automatically maintains a "hot" or "active" disk area likely
318 to be written to again soon based on the recent write activity. The
319 "active" disk area can be written to immediately, while "inactive"
320 disk areas must be "activated" first, which requires a meta-data
321 write. We also refer to this active disk area as the "activity
322 log".
323 The activity log saves meta-data writes, but the whole log must be
325 resynced upon recovery of a failed node. The size of the activity
326 log is a major factor of how long a resync will take and how fast a
327 replicated disk will become consistent after a crash.
328 The activity log consists of a number of 4-Megabyte segments; the
330 al-extents parameter determines how many of those segments can be
331 active at the same time. The default value for al-extents is 1237,
332 with a minimum of 7 and a maximum of 65536.
333 Note that the effective maximum may be smaller, depending on how
335 you created the device meta data, see also drbdmeta(8) The
336 effective maximum is 919 * (available on-disk activity-log
337 ring-buffer area/4kB -1), the default 32kB ring-buffer effects a
338 maximum of 6433 (covers more than 25 GiB of data) We recommend to
339 keep this well within the amount your backend storage and
340 replication link are able to resync inside of about 5 minutes.
341 al-updates {yes | no}
343 With this parameter, the activity log can be turned off entirely
345 (see the al-extents parameter). This will speed up writes because
346 fewer meta-data writes will be necessary, but the entire device
347 needs to be resynchronized opon recovery of a failed primary node.
348 The default value for al-updates is yes.
349 disk-barrier,
351 disk-flushes,
352 disk-drain
353 DRBD has three methods of handling the ordering of dependent write
354 requests:
355 disk-barrier
357 Use disk barriers to make sure that requests are written to
358 disk in the right order. Barriers ensure that all requests
359 submitted before a barrier make it to the disk before any
360 requests submitted after the barrier. This is implemented using
361 'tagged command queuing' on SCSI devices and 'native command
362 queuing' on SATA devices. Only some devices and device stacks
363 support this method. The device mapper (LVM) only supports
364 barriers in some configurations.
365 Note that on systems which do not support disk barriers,
367 enabling this option can lead to data loss or corruption. Until
368 DRBD 8.4.1, disk-barrier was turned on if the I/O stack below
369 DRBD did support barriers. Kernels since linux-2.6.36 (or
370 2.6.32 RHEL6) no longer allow to detect if barriers are
371 supported. Since drbd-8.4.2, this option is off by default and
372 needs to be enabled explicitly.
373 disk-flushes
375 Use disk flushes between dependent write requests, also
376 referred to as 'force unit access' by drive vendors. This
377 forces all data to disk. This option is enabled by default.
378 disk-drain
380 Wait for the request queue to "drain" (that is, wait for the
381 requests to finish) before submitting a dependent write
382 request. This method requires that requests are stable on disk
383 when they finish. Before DRBD 8.0.9, this was the only method
384 implemented. This option is enabled by default. Do not disable
385 in production environments.
386 From these three methods, drbd will use the first that is enabled
388 and supported by the backing storage device. If all three of these
389 options are turned off, DRBD will submit write requests without
390 bothering about dependencies. Depending on the I/O stack, write
391 requests can be reordered, and they can be submitted in a different
392 order on different cluster nodes. This can result in data loss or
393 corruption. Therefore, turning off all three methods of controlling
394 write ordering is strongly discouraged.
395 A general guideline for configuring write ordering is to use disk
397 barriers or disk flushes when using ordinary disks (or an ordinary
398 disk array) with a volatile write cache. On storage without cache
399 or with a battery backed write cache, disk draining can be a
400 reasonable choice.
401 disk-timeout
403 If the lower-level device on which a DRBD device stores its data
404 does not finish an I/O request within the defined disk-timeout,
405 DRBD treats this as a failure. The lower-level device is detached,
406 and the device's disk state advances to Diskless. If DRBD is
407 connected to one or more peers, the failed request is passed on to
408 one of them.
409 This option is dangerous and may lead to kernel panic!
411 "Aborting" requests, or force-detaching the disk, is intended for
413 completely blocked/hung local backing devices which do no longer
414 complete requests at all, not even do error completions. In this
415 situation, usually a hard-reset and failover is the only way out.
416 By "aborting", basically faking a local error-completion, we allow
418 for a more graceful swichover by cleanly migrating services. Still
419 the affected node has to be rebooted "soon".
420 By completing these requests, we allow the upper layers to re-use
422 the associated data pages.
423 If later the local backing device "recovers", and now DMAs some
425 data from disk into the original request pages, in the best case it
426 will just put random data into unused pages; but typically it will
427 corrupt meanwhile completely unrelated data, causing all sorts of
428 damage.
429 Which means delayed successful completion, especially for READ
431 requests, is a reason to panic(). We assume that a delayed *error*
432 completion is OK, though we still will complain noisily about it.
433 The default value of disk-timeout is 0, which stands for an
435 infinite timeout. Timeouts are specified in units of 0.1 seconds.
436 This option is available since DRBD 8.3.12.
437 md-flushes
439 Enable disk flushes and disk barriers on the meta-data device. This
440 option is enabled by default. See the disk-flushes parameter.
441 on-io-error handler
443 Configure how DRBD reacts to I/O errors on a lower-level device.
445 The following policies are defined:
446 pass_on
448 Change the disk status to Inconsistent, mark the failed block
449 as inconsistent in the bitmap, and retry the I/O operation on a
450 remote cluster node.
451 call-local-io-error
453 Call the local-io-error handler (see the handlers section).
454 detach
456 Detach the lower-level device and continue in diskless mode.
457 read-balancing policy
460 Distribute read requests among cluster nodes as defined by policy.
461 The supported policies are prefer-local (the default),
462 prefer-remote, round-robin, least-pending, when-congested-remote,
463 32K-striping, 64K-striping, 128K-striping, 256K-striping,
464 512K-striping and 1M-striping.
465 This option is available since DRBD 8.4.1.
467 resync-after res-name/volume
469 Define that a device should only resynchronize after the specified
471 other device. By default, no order between devices is defined, and
472 all devices will resynchronize in parallel. Depending on the
473 configuration of the lower-level devices, and the available network
474 and disk bandwidth, this can slow down the overall resync process.
475 This option can be used to form a chain or tree of dependencies
476 among devices.
477 rs-discard-granularity byte
479 When rs-discard-granularity is set to a non zero, positive value
480 then DRBD tries to do a resync operation in requests of this size.
481 In case such a block contains only zero bytes on the sync source
482 node, the sync target node will issue a discard/trim/unmap command
483 for the area.
484 The value is constrained by the discard granularity of the backing
486 block device. In case rs-discard-granularity is not a multiplier of
487 the discard granularity of the backing block device DRBD rounds it
488 up. The feature only gets active if the backing block device reads
489 back zeroes after a discard command.
490 The default value of is 0. This option is available since 8.4.7.
492 discard-zeroes-if-aligned {yes | no}
494 There are several aspects to discard/trim/unmap support on linux
496 block devices. Even if discard is supported in general, it may fail
497 silently, or may partially ignore discard requests. Devices also
498 announce whether reading from unmapped blocks returns defined data
499 (usually zeroes), or undefined data (possibly old data, possibly
500 garbage).
501 If on different nodes, DRBD is backed by devices with differing
503 discard characteristics, discards may lead to data divergence (old
504 data or garbage left over on one backend, zeroes due to unmapped
505 areas on the other backend). Online verify would now potentially
506 report tons of spurious differences. While probably harmless for
507 most use cases (fstrim on a file system), DRBD cannot have that.
508 To play safe, we have to disable discard support, if our local
510 backend (on a Primary) does not support "discard_zeroes_data=true".
511 We also have to translate discards to explicit zero-out on the
512 receiving side, unless the receiving side (Secondary) supports
513 "discard_zeroes_data=true", thereby allocating areas what were
514 supposed to be unmapped.
515 There are some devices (notably the LVM/DM thin provisioning) that
517 are capable of discard, but announce discard_zeroes_data=false. In
518 the case of DM-thin, discards aligned to the chunk size will be
519 unmapped, and reading from unmapped sectors will return zeroes.
520 However, unaligned partial head or tail areas of discard requests
521 will be silently ignored.
522 If we now add a helper to explicitly zero-out these unaligned
524 partial areas, while passing on the discard of the aligned full
525 chunks, we effectively achieve discard_zeroes_data=true on such
526 devices.
527 Setting discard-zeroes-if-aligned to yes will allow DRBD to use
529 discards, and to announce discard_zeroes_data=true, even on
530 backends that announce discard_zeroes_data=false.
531 Setting discard-zeroes-if-aligned to no will cause DRBD to always
533 fall-back to zero-out on the receiving side, and to not even
534 announce discard capabilities on the Primary, if the respective
535 backend announces discard_zeroes_data=false.
536 We used to ignore the discard_zeroes_data setting completely. To
538 not break established and expected behaviour, and suddenly cause
539 fstrim on thin-provisioned LVs to run out-of-space instead of
540 freeing up space, the default value is yes.
541 This option is available since 8.4.7.
543 Section peer-device-options Parameters
545 Please note that you open the section with the disk keyword.
546 c-delay-target delay_target,
548 c-fill-target fill_target,
549 c-max-rate max_rate,
550 c-plan-ahead plan_time
551 Dynamically control the resync speed. The following modes are
552 available:
553 · Dynamic control with fill target (default). Enabled when
555 c-plan-ahead is non-zero and c-fill-target is non-zero. The
556 goal is to fill the buffers along the data path with a defined
557 amount of data. This mode is recommended when DRBD-proxy is
558 used. Configured with c-plan-ahead, c-fill-target and
559 c-max-rate.
560 · Dynamic control with delay target. Enabled when c-plan-ahead is
562 non-zero (default) and c-fill-target is zero. The goal is to
563 have a defined delay along the path. Configured with
564 c-plan-ahead, c-delay-target and c-max-rate.
565 · Fixed resync rate. Enabled when c-plan-ahead is zero. DRBD will
567 try to perform resync I/O at a fixed rate. Configured with
568 resync-rate.
569 The c-plan-ahead parameter defines how fast DRBD adapts to changes
571 in the resync speed. It should be set to five times the network
572 round-trip time or more. The default value of c-plan-ahead is 20,
573 in units of 0.1 seconds.
574 The c-fill-target parameter defines the how much resync data DRBD
576 should aim to have in-flight at all times. Common values for
577 "normal" data paths range from 4K to 100K. The default value of
578 c-fill-target is 100, in units of sectors
579 The c-delay-target parameter defines the delay in the resync path
581 that DRBD should aim for. This should be set to five times the
582 network round-trip time or more. The default value of
583 c-delay-target is 10, in units of 0.1 seconds.
584 The c-max-rate parameter limits the maximum bandwidth used by
586 dynamically controlled resyncs. Setting this to zero removes the
587 limitation (since DRBD 9.0.28). It should be set to either the
588 bandwidth available between the DRBD hosts and the machines hosting
589 DRBD-proxy, or to the available disk bandwidth. The default value
590 of c-max-rate is 102400, in units of KiB/s.
591 Dynamic resync speed control is available since DRBD 8.3.9.
593 c-min-rate min_rate
595 A node which is primary and sync-source has to schedule application
596 I/O requests and resync I/O requests. The c-min-rate parameter
597 limits how much bandwidth is available for resync I/O; the
598 remaining bandwidth is used for application I/O.
599 A c-min-rate value of 0 means that there is no limit on the resync
601 I/O bandwidth. This can slow down application I/O significantly.
602 Use a value of 1 (1 KiB/s) for the lowest possible resync rate.
603 The default value of c-min-rate is 250, in units of KiB/s.
605 resync-rate rate
607 Define how much bandwidth DRBD may use for resynchronizing. DRBD
609 allows "normal" application I/O even during a resync. If the resync
610 takes up too much bandwidth, application I/O can become very slow.
611 This parameter allows to avoid that. Please note this is option
612 only works when the dynamic resync controller is disabled.
613 Section global Parameters
615 dialog-refresh time
616 The DRBD init script can be used to configure and start DRBD
618 devices, which can involve waiting for other cluster nodes. While
619 waiting, the init script shows the remaining waiting time. The
620 dialog-refresh defines the number of seconds between updates of
621 that countdown. The default value is 1; a value of 0 turns off the
622 countdown.
623 disable-ip-verification
625 Normally, DRBD verifies that the IP addresses in the configuration
626 match the host names. Use the disable-ip-verification parameter to
627 disable these checks.
628 usage-count {yes | no | ask}
630 A explained on DRBD's Online Usage Counter[2] web page, DRBD
631 includes a mechanism for anonymously counting how many
632 installations are using which versions of DRBD. The results are
633 available on the web page for anyone to see.
634 This parameter defines if a cluster node participates in the usage
636 counter; the supported values are yes, no, and ask (ask the user,
637 the default).
638 We would like to ask users to participate in the online usage
640 counter as this provides us valuable feedback for steering the
641 development of DRBD.
642 udev-always-use-vnr
644 When udev asks drbdadm for a list of device related symlinks,
645 drbdadm would suggest symlinks with differing naming conventions,
646 depending on whether the resource has explicit volume VNR { }
647 definitions, or only one single volume with the implicit volume
648 number 0:
649 # implicit single volume without "volume 0 {}" block
651 DEVICE=drbd<minor>
652 SYMLINK_BY_RES=drbd/by-res/<resource-name>
653 SYMLINK_BY_DISK=drbd/by-disk/<backing-disk-name>
654 # explicit volume definition: volume VNR { }
656 DEVICE=drbd<minor>
657 SYMLINK_BY_RES=drbd/by-res/<resource-name>/VNR
658 SYMLINK_BY_DISK=drbd/by-disk/<backing-disk-name>
659 If you define this parameter in the global section, drbdadm will
661 always add the .../VNR part, and will not care for whether the
662 volume definition was implicit or explicit.
663 For legacy backward compatibility, this is off by default, but we
665 do recommend to enable it.
666 Section handlers Parameters
668 after-resync-target cmd
669 Called on a resync target when a node state changes from
671 Inconsistent to Consistent when a resync finishes. This handler can
672 be used for removing the snapshot created in the
673 before-resync-target handler.
674 before-resync-target cmd
676 Called on a resync target before a resync begins. This handler can
678 be used for creating a snapshot of the lower-level device for the
679 duration of the resync: if the resync source becomes unavailable
680 during a resync, reverting to the snapshot can restore a consistent
681 state.
682 before-resync-source cmd
684 Called on a resync source before a resync begins.
686 out-of-sync cmd
688 Called on all nodes after a verify finishes and out-of-sync blocks
690 were found. This handler is mainly used for monitoring purposes. An
691 example would be to call a script that sends an alert SMS.
692 quorum-lost cmd
694 Called on a Primary that lost quorum. This handler is usually used
696 to reboot the node if it is not possible to restart the application
697 that uses the storage on top of DRBD.
698 fence-peer cmd
700 Called when a node should fence a resource on a particular peer.
702 The handler should not use the same communication path that DRBD
703 uses for talking to the peer.
704 unfence-peer cmd
706 Called when a node should remove fencing constraints from other
708 nodes.
709 initial-split-brain cmd
711 Called when DRBD connects to a peer and detects that the peer is in
713 a split-brain state with the local node. This handler is also
714 called for split-brain scenarios which will be resolved
715 automatically.
716 local-io-error cmd
718 Called when an I/O error occurs on a lower-level device.
720 pri-lost cmd
722 The local node is currently primary, but DRBD believes that it
724 should become a sync target. The node should give up its primary
725 role.
726 pri-lost-after-sb cmd
728 The local node is currently primary, but it has lost the
730 after-split-brain auto recovery procedure. The node should be
731 abandoned.
732 pri-on-incon-degr cmd
734 The local node is primary, and neither the local lower-level device
736 nor a lower-level device on a peer is up to date. (The primary has
737 no device to read from or to write to.)
738 split-brain cmd
740 DRBD has detected a split-brain situation which could not be
742 resolved automatically. Manual recovery is necessary. This handler
743 can be used to call for administrator attention.
744 disconnected cmd
746 A connection to a peer went down. The handler can learn about the
748 reason for the disconnect from the DRBD_CSTATE environment
749 variable.
750 Section net Parameters
752 after-sb-0pri policy
753 Define how to react if a split-brain scenario is detected and none
754 of the two nodes is in primary role. (We detect split-brain
755 scenarios when two nodes connect; split-brain decisions are always
756 between two nodes.) The defined policies are:
757 disconnect
759 No automatic resynchronization; simply disconnect.
760 discard-younger-primary,
762 discard-older-primary
763 Resynchronize from the node which became primary first
764 (discard-younger-primary) or last (discard-older-primary). If
765 both nodes became primary independently, the
766 discard-least-changes policy is used.
767 discard-zero-changes
769 If only one of the nodes wrote data since the split brain
770 situation was detected, resynchronize from this node to the
771 other. If both nodes wrote data, disconnect.
772 discard-least-changes
774 Resynchronize from the node with more modified blocks.
775 discard-node-nodename
777 Always resynchronize to the named node.
778 after-sb-1pri policy
780 Define how to react if a split-brain scenario is detected, with one
781 node in primary role and one node in secondary role. (We detect
782 split-brain scenarios when two nodes connect, so split-brain
783 decisions are always among two nodes.) The defined policies are:
784 disconnect
786 No automatic resynchronization, simply disconnect.
787 consensus
789 Discard the data on the secondary node if the after-sb-0pri
790 algorithm would also discard the data on the secondary node.
791 Otherwise, disconnect.
792 violently-as0p
794 Always take the decision of the after-sb-0pri algorithm, even
795 if it causes an erratic change of the primary's view of the
796 data. This is only useful if a single-node file system (i.e.,
797 not OCFS2 or GFS) with the allow-two-primaries flag is used.
798 This option can cause the primary node to crash, and should not
799 be used.
800 discard-secondary
802 Discard the data on the secondary node.
803 call-pri-lost-after-sb
805 Always take the decision of the after-sb-0pri algorithm. If the
806 decision is to discard the data on the primary node, call the
807 pri-lost-after-sb handler on the primary node.
808 after-sb-2pri policy
810 Define how to react if a split-brain scenario is detected and both
811 nodes are in primary role. (We detect split-brain scenarios when
812 two nodes connect, so split-brain decisions are always among two
813 nodes.) The defined policies are:
814 disconnect
816 No automatic resynchronization, simply disconnect.
817 violently-as0p
819 See the violently-as0p policy for after-sb-1pri.
820 call-pri-lost-after-sb
822 Call the pri-lost-after-sb helper program on one of the
823 machines unless that machine can demote to secondary. The
824 helper program is expected to reboot the machine, which brings
825 the node into a secondary role. Which machine runs the helper
826 program is determined by the after-sb-0pri strategy.
827 allow-two-primaries
829 The most common way to configure DRBD devices is to allow only one
831 node to be primary (and thus writable) at a time.
832 In some scenarios it is preferable to allow two nodes to be primary
834 at once; a mechanism outside of DRBD then must make sure that
835 writes to the shared, replicated device happen in a coordinated
836 way. This can be done with a shared-storage cluster file system
837 like OCFS2 and GFS, or with virtual machine images and a virtual
838 machine manager that can migrate virtual machines between physical
839 machines.
840 The allow-two-primaries parameter tells DRBD to allow two nodes to
842 be primary at the same time. Never enable this option when using a
843 non-distributed file system; otherwise, data corruption and node
844 crashes will result!
845 always-asbp
847 Normally the automatic after-split-brain policies are only used if
848 current states of the UUIDs do not indicate the presence of a third
849 node.
850 With this option you request that the automatic after-split-brain
852 policies are used as long as the data sets of the nodes are somehow
853 related. This might cause a full sync, if the UUIDs indicate the
854 presence of a third node. (Or double faults led to strange UUID
855 sets.)
856 connect-int time
858 As soon as a connection between two nodes is configured with
860 drbdsetup connect, DRBD immediately tries to establish the
861 connection. If this fails, DRBD waits for connect-int seconds and
862 then repeats. The default value of connect-int is 10 seconds.
863 cram-hmac-alg hash-algorithm
865 Configure the hash-based message authentication code (HMAC) or
867 secure hash algorithm to use for peer authentication. The kernel
868 supports a number of different algorithms, some of which may be
869 loadable as kernel modules. See the shash algorithms listed in
870 /proc/crypto. By default, cram-hmac-alg is unset. Peer
871 authentication also requires a shared-secret to be configured.
872 csums-alg hash-algorithm
874 Normally, when two nodes resynchronize, the sync target requests a
876 piece of out-of-sync data from the sync source, and the sync source
877 sends the data. With many usage patterns, a significant number of
878 those blocks will actually be identical.
879 When a csums-alg algorithm is specified, when requesting a piece of
881 out-of-sync data, the sync target also sends along a hash of the
882 data it currently has. The sync source compares this hash with its
883 own version of the data. It sends the sync target the new data if
884 the hashes differ, and tells it that the data are the same
885 otherwise. This reduces the network bandwidth required, at the cost
886 of higher cpu utilization and possibly increased I/O on the sync
887 target.
888 The csums-alg can be set to one of the secure hash algorithms
890 supported by the kernel; see the shash algorithms listed in
891 /proc/crypto. By default, csums-alg is unset.
892 csums-after-crash-only
894 Enabling this option (and csums-alg, above) makes it possible to
896 use the checksum based resync only for the first resync after
897 primary crash, but not for later "network hickups".
898 In most cases, block that are marked as need-to-be-resynced are in
900 fact changed, so calculating checksums, and both reading and
901 writing the blocks on the resync target is all effective overhead.
902 The advantage of checksum based resync is mostly after primary
904 crash recovery, where the recovery marked larger areas (those
905 covered by the activity log) as need-to-be-resynced, just in case.
906 Introduced in 8.4.5.
907 data-integrity-alg alg
909 DRBD normally relies on the data integrity checks built into the
910 TCP/IP protocol, but if a data integrity algorithm is configured,
911 it will additionally use this algorithm to make sure that the data
912 received over the network match what the sender has sent. If a data
913 integrity error is detected, DRBD will close the network connection
914 and reconnect, which will trigger a resync.
915 The data-integrity-alg can be set to one of the secure hash
917 algorithms supported by the kernel; see the shash algorithms listed
918 in /proc/crypto. By default, this mechanism is turned off.
919 Because of the CPU overhead involved, we recommend not to use this
921 option in production environments. Also see the notes on data
922 integrity below.
923 fencing fencing_policy
925 Fencing is a preventive measure to avoid situations where both
927 nodes are primary and disconnected. This is also known as a
928 split-brain situation. DRBD supports the following fencing
929 policies:
930 dont-care
932 No fencing actions are taken. This is the default policy.
933 resource-only
935 If a node becomes a disconnected primary, it tries to fence the
936 peer. This is done by calling the fence-peer handler. The
937 handler is supposed to reach the peer over an alternative
938 communication path and call 'drbdadm outdate minor' there.
939 resource-and-stonith
941 If a node becomes a disconnected primary, it freezes all its IO
942 operations and calls its fence-peer handler. The fence-peer
943 handler is supposed to reach the peer over an alternative
944 communication path and call 'drbdadm outdate minor' there. In
945 case it cannot do that, it should stonith the peer. IO is
946 resumed as soon as the situation is resolved. In case the
947 fence-peer handler fails, I/O can be resumed manually with
948 'drbdadm resume-io'.
949 ko-count number
951 If a secondary node fails to complete a write request in ko-count
953 times the timeout parameter, it is excluded from the cluster. The
954 primary node then sets the connection to this secondary node to
955 Standalone. To disable this feature, you should explicitly set it
956 to 0; defaults may change between versions.
957 max-buffers number
959 Limits the memory usage per DRBD minor device on the receiving
961 side, or for internal buffers during resync or online-verify. Unit
962 is PAGE_SIZE, which is 4 KiB on most systems. The minimum possible
963 setting is hard coded to 32 (=128 KiB). These buffers are used to
964 hold data blocks while they are written to/read from disk. To avoid
965 possible distributed deadlocks on congestion, this setting is used
966 as a throttle threshold rather than a hard limit. Once more than
967 max-buffers pages are in use, further allocation from this pool is
968 throttled. You want to increase max-buffers if you cannot saturate
969 the IO backend on the receiving side.
970 max-epoch-size number
972 Define the maximum number of write requests DRBD may issue before
974 issuing a write barrier. The default value is 2048, with a minimum
975 of 1 and a maximum of 20000. Setting this parameter to a value
976 below 10 is likely to decrease performance.
977 on-congestion policy,
979 congestion-fill threshold,
980 congestion-extents threshold
981 By default, DRBD blocks when the TCP send queue is full. This
982 prevents applications from generating further write requests until
983 more buffer space becomes available again.
984 When DRBD is used together with DRBD-proxy, it can be better to use
986 the pull-ahead on-congestion policy, which can switch DRBD into
987 ahead/behind mode before the send queue is full. DRBD then records
988 the differences between itself and the peer in its bitmap, but it
989 no longer replicates them to the peer. When enough buffer space
990 becomes available again, the node resynchronizes with the peer and
991 switches back to normal replication.
992 This has the advantage of not blocking application I/O even when
994 the queues fill up, and the disadvantage that peer nodes can fall
995 behind much further. Also, while resynchronizing, peer nodes will
996 become inconsistent.
997 The available congestion policies are block (the default) and
999 pull-ahead. The congestion-fill parameter defines how much data is
1000 allowed to be "in flight" in this connection. The default value is
1001 0, which disables this mechanism of congestion control, with a
1002 maximum of 10 GiBytes. The congestion-extents parameter defines how
1003 many bitmap extents may be active before switching into
1004 ahead/behind mode, with the same default and limits as the
1005 al-extents parameter. The congestion-extents parameter is effective
1006 only when set to a value smaller than al-extents.
1007 Ahead/behind mode is available since DRBD 8.3.10.
1009 ping-int interval
1011 When the TCP/IP connection to a peer is idle for more than ping-int
1013 seconds, DRBD will send a keep-alive packet to make sure that a
1014 failed peer or network connection is detected reasonably soon. The
1015 default value is 10 seconds, with a minimum of 1 and a maximum of
1016 120 seconds. The unit is seconds.
1017 ping-timeout timeout
1019 Define the timeout for replies to keep-alive packets. If the peer
1021 does not reply within ping-timeout, DRBD will close and try to
1022 reestablish the connection. The default value is 0.5 seconds, with
1023 a minimum of 0.1 seconds and a maximum of 3 seconds. The unit is
1024 tenths of a second.
1025 socket-check-timeout timeout
1027 In setups involving a DRBD-proxy and connections that experience a
1028 lot of buffer-bloat it might be necessary to set ping-timeout to an
1029 unusual high value. By default DRBD uses the same value to wait if
1030 a newly established TCP-connection is stable. Since the DRBD-proxy
1031 is usually located in the same data center such a long wait time
1032 may hinder DRBD's connect process.
1033 In such setups socket-check-timeout should be set to at least to
1035 the round trip time between DRBD and DRBD-proxy. I.e. in most cases
1036 to 1.
1037 The default unit is tenths of a second, the default value is 0
1039 (which causes DRBD to use the value of ping-timeout instead).
1040 Introduced in 8.4.5.
1041 protocol name
1043 Use the specified protocol on this connection. The supported
1044 protocols are:
1045 A
1047 Writes to the DRBD device complete as soon as they have reached
1048 the local disk and the TCP/IP send buffer.
1049 B
1051 Writes to the DRBD device complete as soon as they have reached
1052 the local disk, and all peers have acknowledged the receipt of
1053 the write requests.
1054 C
1056 Writes to the DRBD device complete as soon as they have reached
1057 the local and all remote disks.
1058 rcvbuf-size size
1061 Configure the size of the TCP/IP receive buffer. A value of 0 (the
1063 default) causes the buffer size to adjust dynamically. This
1064 parameter usually does not need to be set, but it can be set to a
1065 value up to 10 MiB. The default unit is bytes.
1066 rr-conflict policy
1068 This option helps to solve the cases when the outcome of the resync
1069 decision is incompatible with the current role assignment in the
1070 cluster. The defined policies are:
1071 disconnect
1073 No automatic resynchronization, simply disconnect.
1074 retry-connect
1076 Disconnect now, and retry to connect immediatly afterwards.
1077 violently
1079 Resync to the primary node is allowed, violating the assumption
1080 that data on a block device are stable for one of the nodes.
1081 Do not use this option, it is dangerous.
1082 call-pri-lost
1084 Call the pri-lost handler on one of the machines. The handler
1085 is expected to reboot the machine, which puts it into secondary
1086 role.
1087 shared-secret secret
1089 Configure the shared secret used for peer authentication. The
1091 secret is a string of up to 64 characters. Peer authentication also
1092 requires the cram-hmac-alg parameter to be set.
1093 sndbuf-size size
1095 Configure the size of the TCP/IP send buffer. Since DRBD 8.0.13 /
1097 8.2.7, a value of 0 (the default) causes the buffer size to adjust
1098 dynamically. Values below 32 KiB are harmful to the throughput on
1099 this connection. Large buffer sizes can be useful especially when
1100 protocol A is used over high-latency networks; the maximum value
1101 supported is 10 MiB.
1102 tcp-cork
1104 By default, DRBD uses the TCP_CORK socket option to prevent the
1105 kernel from sending partial messages; this results in fewer and
1106 bigger packets on the network. Some network stacks can perform
1107 worse with this optimization. On these, the tcp-cork parameter can
1108 be used to turn this optimization off.
1109 timeout time
1111 Define the timeout for replies over the network: if a peer node
1113 does not send an expected reply within the specified timeout, it is
1114 considered dead and the TCP/IP connection is closed. The timeout
1115 value must be lower than connect-int and lower than ping-int. The
1116 default is 6 seconds; the value is specified in tenths of a second.
1117 transport type
1119 With DRBD9 the network transport used by DRBD is loaded as a
1121 seperate module. With this option you can specify which transport
1122 and module to load. At present only two options exist, tcp and
1123 rdma. Please note that currently the RDMA transport module is only
1124 available with a license purchased from LINBIT. Default is tcp.
1125 use-rle
1127 Each replicated device on a cluster node has a separate bitmap for
1129 each of its peer devices. The bitmaps are used for tracking the
1130 differences between the local and peer device: depending on the
1131 cluster state, a disk range can be marked as different from the
1132 peer in the device's bitmap, in the peer device's bitmap, or in
1133 both bitmaps. When two cluster nodes connect, they exchange each
1134 other's bitmaps, and they each compute the union of the local and
1135 peer bitmap to determine the overall differences.
1136 Bitmaps of very large devices are also relatively large, but they
1138 usually compress very well using run-length encoding. This can save
1139 time and bandwidth for the bitmap transfers.
1140 The use-rle parameter determines if run-length encoding should be
1142 used. It is on by default since DRBD 8.4.0.
1143 verify-alg hash-algorithm
1145 Online verification (drbdadm verify) computes and compares
1146 checksums of disk blocks (i.e., hash values) in order to detect if
1147 they differ. The verify-alg parameter determines which algorithm to
1148 use for these checksums. It must be set to one of the secure hash
1149 algorithms supported by the kernel before online verify can be
1150 used; see the shash algorithms listed in /proc/crypto.
1151 We recommend to schedule online verifications regularly during
1153 low-load periods, for example once a month. Also see the notes on
1154 data integrity below.
1155 allow-remote-read bool-value
1157 Allows or disallows DRBD to read from a peer node.
1158 When the disk of a primary node is detached, DRBD will try to
1160 continue reading and writing from another node in the cluster. For
1161 this purpose, it searches for nodes with up-to-date data, and uses
1162 any found node to resume operations. In some cases it may not be
1163 desirable to read back data from a peer node, because the node
1164 should only be used as a replication target. In this case, the
1165 allow-remote-read parameter can be set to no, which would prohibit
1166 this node from reading data from the peer node.
1167 The allow-remote-read parameter is available since DRBD 9.0.19, and
1169 defaults to yes.
1170 Section on Parameters
1172 address [address-family] address:port
1173 Defines the address family, address, and port of a connection
1175 endpoint.
1176 The address families ipv4, ipv6, ssocks (Dolphin Interconnect
1178 Solutions' "super sockets"), sdp (Infiniband Sockets Direct
1179 Protocol), and sci are supported (sci is an alias for ssocks). If
1180 no address family is specified, ipv4 is assumed. For all address
1181 families except ipv6, the address is specified in IPV4 address
1182 notation (for example, 1.2.3.4). For ipv6, the address is enclosed
1183 in brackets and uses IPv6 address notation (for example,
1184 [fd01:2345:6789:abcd::1]). The port is always specified as a
1185 decimal number from 1 to 65535.
1186 On each host, the port numbers must be unique for each address;
1188 ports cannot be shared.
1189 node-id value
1191 Defines the unique node identifier for a node in the cluster. Node
1193 identifiers are used to identify individual nodes in the network
1194 protocol, and to assign bitmap slots to nodes in the metadata.
1195 Node identifiers can only be reasssigned in a cluster when the
1197 cluster is down. It is essential that the node identifiers in the
1198 configuration and in the device metadata are changed consistently
1199 on all hosts. To change the metadata, dump the current state with
1200 drbdmeta dump-md, adjust the bitmap slot assignment, and update the
1201 metadata with drbdmeta restore-md.
1202 The node-id parameter exists since DRBD 9. Its value ranges from 0
1204 to 16; there is no default.
1205 Section options Parameters (Resource Options)
1207 auto-promote bool-value
1208 A resource must be promoted to primary role before any of its
1209 devices can be mounted or opened for writing.
1210 Before DRBD 9, this could only be done explicitly ("drbdadm
1212 primary"). Since DRBD 9, the auto-promote parameter allows to
1213 automatically promote a resource to primary role when one of its
1214 devices is mounted or opened for writing. As soon as all devices
1215 are unmounted or closed with no more remaining users, the role of
1216 the resource changes back to secondary.
1217 Automatic promotion only succeeds if the cluster state allows it
1219 (that is, if an explicit drbdadm primary command would succeed).
1220 Otherwise, mounting or opening the device fails as it already did
1221 before DRBD 9: the mount(2) system call fails with errno set to
1222 EROFS (Read-only file system); the open(2) system call fails with
1223 errno set to EMEDIUMTYPE (wrong medium type).
1224 Irrespective of the auto-promote parameter, if a device is promoted
1226 explicitly (drbdadm primary), it also needs to be demoted
1227 explicitly (drbdadm secondary).
1228 The auto-promote parameter is available since DRBD 9.0.0, and
1230 defaults to yes.
1231 cpu-mask cpu-mask
1233 Set the cpu affinity mask for DRBD kernel threads. The cpu mask is
1235 specified as a hexadecimal number. The default value is 0, which
1236 lets the scheduler decide which kernel threads run on which CPUs.
1237 CPU numbers in cpu-mask which do not exist in the system are
1238 ignored.
1239 on-no-data-accessible policy
1241 Determine how to deal with I/O requests when the requested data is
1242 not available locally or remotely (for example, when all disks have
1243 failed). The defined policies are:
1244 io-error
1246 System calls fail with errno set to EIO.
1247 suspend-io
1249 The resource suspends I/O. I/O can be resumed by (re)attaching
1250 the lower-level device, by connecting to a peer which has
1251 access to the data, or by forcing DRBD to resume I/O with
1252 drbdadm resume-io res. When no data is available, forcing I/O
1253 to resume will result in the same behavior as the io-error
1254 policy.
1255 This setting is available since DRBD 8.3.9; the default policy is
1257 io-error.
1258 peer-ack-window value
1260 On each node and for each device, DRBD maintains a bitmap of the
1262 differences between the local and remote data for each peer device.
1263 For example, in a three-node setup (nodes A, B, C) each with a
1264 single device, every node maintains one bitmap for each of its
1265 peers.
1266 When nodes receive write requests, they know how to update the
1268 bitmaps for the writing node, but not how to update the bitmaps
1269 between themselves. In this example, when a write request
1270 propagates from node A to B and C, nodes B and C know that they
1271 have the same data as node A, but not whether or not they both have
1272 the same data.
1273 As a remedy, the writing node occasionally sends peer-ack packets
1275 to its peers which tell them which state they are in relative to
1276 each other.
1277 The peer-ack-window parameter specifies how much data a primary
1279 node may send before sending a peer-ack packet. A low value causes
1280 increased network traffic; a high value causes less network traffic
1281 but higher memory consumption on secondary nodes and higher resync
1282 times between the secondary nodes after primary node failures.
1283 (Note: peer-ack packets may be sent due to other reasons as well,
1284 e.g. membership changes or expiry of the peer-ack-delay timer.)
1285 The default value for peer-ack-window is 2 MiB, the default unit is
1287 sectors. This option is available since 9.0.0.
1288 peer-ack-delay expiry-time
1290 If after the last finished write request no new write request gets
1292 issued for expiry-time, then a peer-ack packet is sent. If a new
1293 write request is issued before the timer expires, the timer gets
1294 reset to expiry-time. (Note: peer-ack packets may be sent due to
1295 other reasons as well, e.g. membership changes or the
1296 peer-ack-window option.)
1297 This parameter may influence resync behavior on remote nodes. Peer
1299 nodes need to wait until they receive an peer-ack for releasing a
1300 lock on an AL-extent. Resync operations between peers may need to
1301 wait for for these locks.
1302 The default value for peer-ack-delay is 100 milliseconds, the
1304 default unit is milliseconds. This option is available since 9.0.0.
1305 quorum value
1307 When activated, a cluster partition requires quorum in order to
1309 modify the replicated data set. That means a node in the cluster
1310 partition can only be promoted to primary if the cluster partition
1311 has quorum. Every node with a disk directly connected to the node
1312 that should be promoted counts. If a primary node should execute a
1313 write request, but the cluster partition has lost quorum, it will
1314 freeze IO or reject the write request with an error (depending on
1315 the on-no-quorum setting). Upon loosing quorum a primary always
1316 invokes the quorum-lost handler. The handler is intended for
1317 notification purposes, its return code is ignored.
1318 The option's value might be set to off, majority, all or a numeric
1320 value. If you set it to a numeric value, make sure that the value
1321 is greater than half of your number of nodes. Quorum is a mechanism
1322 to avoid data divergence, it might be used instead of fencing when
1323 there are more than two repicas. It defaults to off
1324 If all missing nodes are marked as outdated, a partition always has
1326 quorum, no matter how small it is. I.e. If you disconnect all
1327 secondary nodes gracefully a single primary continues to operate.
1328 In the moment a single secondary is lost, it has to be assumed that
1329 it forms a partition with all the missing outdated nodes. In case
1330 my partition might be smaller than the other, quorum is lost in
1331 this moment.
1332 In case you want to allow permanently diskless nodes to gain quorum
1334 it is recommendet to not use majority or all. It is recommended to
1335 specify an absolute number, since DBRD's heuristic to determine the
1336 complete number of diskfull nodes in the cluster is unreliable.
1337 The quorum implementation is available starting with the DRBD
1339 kernel driver version 9.0.7.
1340 quorum-minimum-redundancy value
1342 This option sets the minimal required number of nodes with an
1344 UpToDate disk to allow the partition to gain quorum. This is a
1345 different requirement than the plain quorum option expresses.
1346 The option's value might be set to off, majority, all or a numeric
1348 value. If you set it to a numeric value, make sure that the value
1349 is greater than half of your number of nodes.
1350 In case you want to allow permanently diskless nodes to gain quorum
1352 it is recommendet to not use majority or all. It is recommended to
1353 specify an absolute number, since DBRD's heuristic to determine the
1354 complete number of diskfull nodes in the cluster is unreliable.
1355 This option is available starting with the DRBD kernel driver
1357 version 9.0.10.
1358 on-no-quorum {io-error | suspend-io}
1360 By default DRBD freezes IO on a device, that lost quorum. By
1362 setting the on-no-quorum to io-error it completes all IO operations
1363 with an error if quorum ist lost.
1364 The on-no-quorum options is available starting with the DRBD kernel
1366 driver version 9.0.8.
1367 Section startup Parameters
1369 The parameters in this section define the behavior of DRBD at system
1370 startup time, in the DRBD init script. They have no effect once the
1371 system is up and running.
1372 degr-wfc-timeout timeout
1374 Define how long to wait until all peers are connected in case the
1376 cluster consisted of a single node only when the system went down.
1377 This parameter is usually set to a value smaller than wfc-timeout.
1378 The assumption here is that peers which were unreachable before a
1379 reboot are less likely to be reachable after the reboot, so waiting
1380 is less likely to help.
1381 The timeout is specified in seconds. The default value is 0, which
1383 stands for an infinite timeout. Also see the wfc-timeout parameter.
1384 outdated-wfc-timeout timeout
1386 Define how long to wait until all peers are connected if all peers
1388 were outdated when the system went down. This parameter is usually
1389 set to a value smaller than wfc-timeout. The assumption here is
1390 that an outdated peer cannot have become primary in the meantime,
1391 so we don't need to wait for it as long as for a node which was
1392 alive before.
1393 The timeout is specified in seconds. The default value is 0, which
1395 stands for an infinite timeout. Also see the wfc-timeout parameter.
1396 stacked-timeouts
1398 On stacked devices, the wfc-timeout and degr-wfc-timeout parameters
1399 in the configuration are usually ignored, and both timeouts are set
1400 to twice the connect-int timeout. The stacked-timeouts parameter
1401 tells DRBD to use the wfc-timeout and degr-wfc-timeout parameters
1402 as defined in the configuration, even on stacked devices. Only use
1403 this parameter if the peer of the stacked resource is usually not
1404 available, or will not become primary. Incorrect use of this
1405 parameter can lead to unexpected split-brain scenarios.
1406 wait-after-sb
1408 This parameter causes DRBD to continue waiting in the init script
1409 even when a split-brain situation has been detected, and the nodes
1410 therefore refuse to connect to each other.
1411 wfc-timeout timeout
1413 Define how long the init script waits until all peers are
1415 connected. This can be useful in combination with a cluster manager
1416 which cannot manage DRBD resources: when the cluster manager
1417 starts, the DRBD resources will already be up and running. With a
1418 more capable cluster manager such as Pacemaker, it makes more sense
1419 to let the cluster manager control DRBD resources. The timeout is
1420 specified in seconds. The default value is 0, which stands for an
1421 infinite timeout. Also see the degr-wfc-timeout parameter.
1422 Section volume Parameters
1424 device /dev/drbdminor-number
1425 Define the device name and minor number of a replicated block
1427 device. This is the device that applications are supposed to
1428 access; in most cases, the device is not used directly, but as a
1429 file system. This parameter is required and the standard device
1430 naming convention is assumed.
1431 In addition to this device, udev will create
1433 /dev/drbd/by-res/resource/volume and
1434 /dev/drbd/by-disk/lower-level-device symlinks to the device.
1435 disk {[disk] | none}
1437 Define the lower-level block device that DRBD will use for storing
1439 the actual data. While the replicated drbd device is configured,
1440 the lower-level device must not be used directly. Even read-only
1441 access with tools like dumpe2fs(8) and similar is not allowed. The
1442 keyword none specifies that no lower-level block device is
1443 configured; this also overrides inheritance of the lower-level
1444 device.
1445 meta-disk internal,
1447 meta-disk device,
1448 meta-disk device [index]
1449 Define where the metadata of a replicated block device resides: it
1451 can be internal, meaning that the lower-level device contains both
1452 the data and the metadata, or on a separate device.
1453 When the index form of this parameter is used, multiple replicated
1455 devices can share the same metadata device, each using a separate
1456 index. Each index occupies 128 MiB of data, which corresponds to a
1457 replicated device size of at most 4 TiB with two cluster nodes. We
1458 recommend not to share metadata devices anymore, and to instead use
1459 the lvm volume manager for creating metadata devices as needed.
1460 When the index form of this parameter is not used, the size of the
1462 lower-level device determines the size of the metadata. The size
1463 needed is 36 KiB + (size of lower-level device) / 32K * (number of
1464 nodes - 1). If the metadata device is bigger than that, the extra
1465 space is not used.
1466 This parameter is required if a disk other than none is specified,
1468 and ignored if disk is set to none. A meta-disk parameter without a
1469 disk parameter is not allowed.
1470
1472 DRBD supports two different mechanisms for data integrity checking:
1473 first, the data-integrity-alg network parameter allows to add a
1474 checksum to the data sent over the network. Second, the online
1475 verification mechanism (drbdadm verify and the verify-alg parameter)
1476 allows to check for differences in the on-disk data.
1477 Both mechanisms can produce false positives if the data is modified
1479 during I/O (i.e., while it is being sent over the network or written to
1480 disk). This does not always indicate a problem: for example, some file
1481 systems and applications do modify data under I/O for certain
1482 operations. Swap space can also undergo changes while under I/O.
1483 Network data integrity checking tries to identify data modification
1485 during I/O by verifying the checksums on the sender side after sending
1486 the data. If it detects a mismatch, it logs an error. The receiver also
1487 logs an error when it detects a mismatch. Thus, an error logged only on
1488 the receiver side indicates an error on the network, and an error
1489 logged on both sides indicates data modification under I/O.
1490 The most recent example of systematic data corruption was identified as
1492 a bug in the TCP offloading engine and driver of a certain type of GBit
1493 NIC in 2007: the data corruption happened on the DMA transfer from core
1494 memory to the card. Because the TCP checksum were calculated on the
1495 card, the TCP/IP protocol checksums did not reveal this problem.
1496
1498 This document was revised for version 9.0.0 of the DRBD distribution.
1499
1501 Written by Philipp Reisner <philipp.reisner@linbit.com> and Lars
1502 Ellenberg <lars.ellenberg@linbit.com>.
1503
1505 Report bugs to <drbd-user@lists.linbit.com>.
1506
1508 Copyright 2001-2018 LINBIT Information Technologies, Philipp Reisner,
1509 Lars Ellenberg. This is free software; see the source for copying
1510 conditions. There is NO warranty; not even for MERCHANTABILITY or
1511 FITNESS FOR A PARTICULAR PURPOSE.
1512
1514 drbd(8), drbdsetup(8), drbdadm(8), DRBD User's Guide[1], DRBD Web
1515 Site[3]
1516
1518 1. DRBD User's Guide
1519 http://www.drbd.org/users-guide/
1520 2.
1522 Online Usage Counter
1524 http://usage.drbd.org
1525 3. DRBD Web Site
1527 http://www.drbd.org/
1528DRBD 9.0.x 17 January 2018 DRBD.CONF(5)