1SG_FORMAT(8) SG3_UTILS SG_FORMAT(8)
2
6 sg_format - format, format with preset, resize SCSI disk; format tape
7
9 sg_format [--cmplst={0|1}] [--count=COUNT] [--dcrt] [--dry-run]
10 [--early] [--ffmt=FFMT] [--fmtmaxlba-fmtpinfo=FPI] [--format] [--help]
11 [--ip-def] [--long] [--mode=MP] [--pfu=PFU] [--pie=PIE] [--pinfo]
12 [--poll=PT] [--preset=ID] [--quick] [--resize] [--rto_req] [--security]
13 [--six] [--size=LB_SZ] [--tape=FM] [--timeout=SECS] [--verbose] [--ver‐
14 ify] [--version] [--wait] DEVICE
15
17 Not all SCSI direct access devices need to be formatted and some have
18 vendor specific formatting procedures. SCSI disks with rotating media
19 are probably the largest group that do support a 'standard' format op‐
20 eration. They are typically factory formatted to a block size of 512
21 bytes with the largest number of blocks that the manufacturer recom‐
22 mends. The manufacturer's recommendation typically leaves aside a cer‐
23 tain number of tracks, spread across the media, for reassignment of
24 blocks to logical block addresses during the life of the disk.
25 This utility issues one of three SCSI format commands: FORMAT UNIT,
27 FORMAT MEDIUM or FORMAT WITH PRESET. In the following description, un‐
28 qualified sections will usually be referring to the SCSI FORMAT UNIT
29 command. Both FORMAT UNIT and FORMAT WITH PRESET apply to disks (or
30 disk-like devices). The FORMAT MEDIUM command is for tapes.
31 This utility can format modern SCSI disks and potentially change their
33 block size (if permitted) and the block count (i.e. number of accessi‐
34 ble blocks on the media also known as "resizing"). Resizing a disk to
35 less than the manufacturer's recommended block count is sometimes
36 called "short stroking" (see NOTES section). Resizing the block count
37 while not changing the block size may not require a format operation.
38 The SBC-2 standard (see www.t10.org) has obsoleted the "format device"
39 mode page. Many of the low level details found in that mode page are
40 now left up to the discretion of the manufacturer. There is a Format
41 Status log page which reports on the previous successful format opera‐
42 tion(s).
43 When this utility is used without options (i.e. it is only given a DE‐
45 VICE argument) it prints out the existing block size and block count
46 derived from two sources. These two sources are a block descriptor in
47 the response to a MODE SENSE command and the response to a READ CAPAC‐
48 ITY command. The reason for this double check is to detect a "format
49 corrupt" state (see the NOTES section). This usage will not modify the
50 disk.
51 When this utility is used with either --format, --preset=ID or
53 --tape=FM, it will attempt to format the given DEVICE. In the absence
54 of the --quick option there is a 15 second pause during which time the
55 user is invited thrice (5 seconds apart) to abort sg_format. This oc‐
56 curs just prior the SCSI FORMAT UNIT, FORMAT WITH PRESET or FORMAT
57 MEDIUM command being issued. See the NOTES section for more informa‐
58 tion.
59 Protection information (PI) is optional and is made up of one or more
61 protection intervals, each made up of 8 bytes associated with a logical
62 block. When PI is active each logical block will have 1, 2, 4, 8, etc
63 protection intervals (i.e. a power of two), interleaved with (and fol‐
64 lowing) the user data to which they refer. Four protection types are
65 defined with protection type 0 being no protection intervals. See the
66 PROTECTION INFORMATION section below for more information.
67 When the --tape=FM option is given then the SCSI FORMAT MEDIUM command
69 is sent to the DEVICE. FORMAT MEDIUM is defined in the SSC documents at
70 T10 and prepares a volume for use. That may include partitioning the
71 medium. See the section below on TAPE for more information.
72 The FORMAT WITH PRESET was added in draft SBC-4 revision 18. A preset
74 pattern, selected by the PRESET IDENTIFIER field (--id=FWPID), is writ‐
75 ten to the disk. See the FORMAT PRESETS VPD page (0xb8) for a list of
76 available Format preset identifiers and their associated data.
77
79 Arguments to long options are mandatory for short options as well. The
80 options are arranged in alphabetical order based on the long option
81 name.
82 -C, --cmplst={0|1}
84 sets the CMPLST ("complete list") bit in the FORMAT UNIT cdb to
85 0 or 1. If the value is 0 then the existing GLIST (grown list)
86 is taken into account. If the value is 1 then the existing
87 GLIST is ignored. CMPLST defaults to 1 apart from when the
88 --ffmt=FFMT option's value is non-zero in which case CMPLST de‐
89 faults to 0. See the LISTS section below. In most cases this bit
90 should be left at its default value.
91 -c, --count=COUNT
93 where COUNT is the number of blocks to be formatted or media to
94 be resized to. Can be used with either --format or --resize.
95 With --format this option need not be given in which case it is
96 assumed to be zero.
97 With --format the interpretation of COUNT is:
98 (COUNT > 0) : only format the first COUNT blocks and READ CA‐
99 PACITY will report COUNT blocks after format
100 (COUNT = 0) and block size unchanged : use existing block
101 count
102 (COUNT = 0) and block size changed : recommended maximum block
103 count for new block size
104 (COUNT = -1) : use recommended maximum block count
105 (COUNT < -1) : illegal
106 With --resize this option must be given and COUNT has this in‐
107 terpretation:
108 (COUNT > 0) : after resize READ CAPACITY will report COUNT
109 blocks
110 (COUNT = 0) : after resize READ CAPACITY will report 0 blocks
111 (COUNT = -1) : after resize READ CAPACITY will report its max‐
112 imum number of blocks
113 (COUNT < -1) : illegal
114 In both cases if the given COUNT exceeds the maximum number of
115 blocks (for the block size) then the disk reports an error. See
116 NOTES section below.
117 -D, --dcrt
119 this option sets the DCRT bit in the FORMAT UNIT command's pa‐
120 rameter list header. It will "disable certification". Certifica‐
121 tion verifies that blocks are usable during the format process.
122 Using this option may speed the format but --ffmt=FFMT, if
123 available, would probably be better. The default action of this
124 utility (i.e. when this option is not given) is to clear the
125 DCRT bit thereby requesting "media certification" (also unless
126 another option needs it, the FOV bit will be cleared). When the
127 DCRT bit is set, the FOV bit must also be set hence sg_format
128 does that.
129 If this option is given twice then certification is enabled by
130 clearing the DCRT bit and setting the FOV bit. Both these bits
131 are found in the parameter list associated with the FORMAT UNIT
132 cdb.
133 -d, --dry-run
135 this option will parse the command line, do all the preparation
136 but bypass the actual FORMAT UNIT, FORMAT WITH PRESET or FORMAT
137 MEDIUM command. Also if the options would otherwise cause the
138 logical block size to change, then the MODE SELECT command that
139 would do that is also bypassed when the dry run option is given.
140 -e, --early
142 during a format operation, The default action of this utility is
143 to poll the disk every 60 seconds (or every 10 seconds if FFMT
144 is non-zero) to determine the progress of the format operation
145 until it is finished. When this option is given this utility
146 will exit "early", that is as soon as the format operation has
147 commenced. Then the user can monitor the progress of the ongoing
148 format operation with other utilities (e.g. sg_turs(8) or sg_re‐
149 quests(8)). This option and --wait are mutually exclusive.
150 -t, --ffmt=FFMT
152 FFMT (fast format) is placed in a field of the same name in the
153 FORMAT UNIT cdb. The field was introduced in SBC-4 revision 10.
154 The default value is 0 which implies the former action which is
155 typically to overwrite all blocks on the DEVICE. That can take a
156 long time (e.g. with hard disks over 10 TB in size that can be
157 days). With FFMT set that time may be reduced to minutes or
158 less. So it is worth trying if it is available.
159 FFMT has values 1 and 2 for fast format with 3 being reserved
160 currently. These two values include this description: "The de‐
161 vice server initializes the medium ... without overwriting the
162 medium (i.e. resources for managing medium access are initial‐
163 ized and the medium is not written)". The difference between 1
164 and 2 concerns read operations on LBAs to which no data has been
165 written to, after the fast format. When FFMT is 1 the read oper‐
166 ation should return "unspecified logical block data" and com‐
167 plete without error. When FFMT is 2 the read operation may yield
168 check condition status with a sense key set to hardware error,
169 medium error or command aborted. See draft SBC-4 revision 16
170 section 4.34 for more details.
171 -b, --fmtmaxlba
173 This option is only active if it is given together with the
174 --preset=ID option. If so it sets the FMTMAXLBA field in the
175 FORMAT WITH PRESET command.
176 -f, --fmtpinfo=FPI
178 sets the FMTPINFO field in the FORMAT UNIT cdb to a value be‐
179 tween 0 and 3. The default value is 0. The FMTPINFO field from
180 SBC-3 revision 16 is a 2 bit field (bits 7 and 6 of byte 1 in
181 the cdb). Prior to that revision it was a single bit field (bit
182 7 of byte 1 in the cdb) and there was an accompanying bit called
183 RTO_REQ (bit 6 of byte 1 in the cdb). The deprecated options
184 "--pinfo" and "--rto-req" represent the older usage. This option
185 should be used in their place. See the PROTECTION INFORMATION
186 section below for more information.
187 -F, --format
189 issue one of the three SCSI "format" commands. In the absence of
190 the --preset=ID and --tape=FM options, the SCSI FORMAT UNIT com‐
191 mand is issued. These commands will destroy all the data held
192 on the media. This option is required to change the block size
193 of a disk. In the absence of the --quick option, the user is
194 given a 15 second count down to ponder the wisdom of doing this,
195 during which time control-C (amongst other Unix commands) can be
196 used to kill this process before it does any damage.
197 When used three times (or more) the preliminary MODE SENSE and
198 SELECT commands are bypassed, leaving only the initial INQUIRY
199 and FORMAT UNIT commands. This is for emergency use (e.g. when
200 the MODE SENSE/SELECT commands are not working) and cannot
201 change the logical block size.
202 See NOTES section for implementation details and EXAMPLES sec‐
203 tion for typical use.
204 -h, --help
206 print out the usage information then exit.
207 -I, --ip-def
209 sets the default Initialization Pattern. Some disks (SSDs) use
210 this to flag that a format should fully provision (i.e. asso‐
211 ciate a physical block with every logical block). The same disks
212 (SSDs) might thin provision if this option is not given. If this
213 option is given then the --security option cannot be given. Also
214 accepts --ip_def for this option.
215 -l, --long
217 the default action of this utility is to assume 32 bit logical
218 block addresses. With 512 byte block size this permits more than
219 2 terabytes (almost 2 ** 41 bytes) on a single disk. This option
220 selects commands and parameters that allow for 64 bit logical
221 block addresses. Specifically this option sets the "longlba"
222 flag in the MODE SENSE (10) command and uses READ CAPACITY (16)
223 rather than READ CAPACITY (10). If this option is not given and
224 READ CAPACITY (10) or MODE SELECT detects a disk the needs more
225 than 32 bits to represent its logical blocks then it is set in‐
226 ternally. This option does not set the LONGLIST bit in the FOR‐
227 MAT UNIT command. The LONGLIST bit is set as required depending
228 other parameters (e.g. when '--pie=PIE' is greater than zero).
229 -M, --mode=MP
231 MP is a mode page number (0 to 62 inclusive) that will be used
232 for reading and perhaps changing the device logical block size.
233 The default is 1 which is the Read-Write Error Recovery mode
234 page.
235 Preferably the chosen (or default) mode page should be saveable
236 (i.e. accept the SP bit set in the MODE SELECT command used
237 when the logical block size is being changed). Recent version of
238 this utility will retry a MODE SELECT if the SP=1 variant fails
239 with a sense key of ILLEGAL REQUEST. That retry will use the
240 same MODE SELECT command but with SP=0 .
241 -P, --pfu=PFU
243 sets the "Protection Field Usage" field in the parameter block
244 associated with a FORMAT UNIT command to PFU. The default value
245 is 0, the only other defined value currently is 1. See the PRO‐
246 TECTION INFORMATION section below for more information.
247 -q, --pie=PIE
249 sets the "Protection Interval Exponent" field in the parameter
250 block associated with a FORMAT UNIT command to PIE. The default
251 value is 0. PIE can only be non-zero with protection types 2
252 and 3. The value of 0 is typical for 512 byte blocks; with 4096
253 byte blocks a value of 3 may be appropriate (i.e. 8 protection
254 intervals interleaved with 4096 bytes of user data). A device
255 may not support any non-zero values. This field first appeared
256 in SBC-3 revision 18.
257 -p, --pinfo
259 this option is deprecated, use the --fmtpinfo=FPI option in‐
260 stead. If used, then it sets bit 7 of byte 1 in the FORMAT UNIT
261 cdb and that is equivalent to setting --fmtpinfo=2. [So if
262 --pinfo is used (plus --fmtpinfo=FPI and --pfu=PFU are not given
263 or their arguments are 0) then protection type 1 is selected.]
264 -x, --poll=PT
266 where PT is the type of poll used. If PT is 0 then a TEST UNIT
267 READY command is used, otherwise a REQUEST SENSE command is
268 used. The default is currently 0 but this will change to 1 in
269 the near future. See the NOTES sections below.
270 -E, --preset=ID
272 this option instructs this utility to issue a SCSI FORMAT WITH
273 PRESET command. The PRESET IDENTIFIER field in that cdb is set
274 to ID. The IMMED field in that cdb is also set unless the --wait
275 option is also given, in which case it is cleared.
276 -Q, --quick
278 the default action (i.e. when the option is not given) is to
279 give the user 15 seconds to reconsider doing a format operation
280 on the DEVICE. When this option is given that step (i.e. the 15
281 second warning period) is skipped.
282 -r, --resize
284 rather than format the disk, it can be resized. This means
285 changing the number of blocks on the device reported by the READ
286 CAPACITY command. This option should be used with the
287 --count=COUNT option. The contents of all logical blocks on the
288 media remain unchanged when this option is used. This means that
289 any resize operation can be reversed. This option cannot be used
290 together with either --format or a --size=LB_SZ whose argument
291 is different to the existing block size.
292 -R, --rto_req
294 The option is deprecated, use the --fmtpinfo=FPI option instead.
295 If used, then it sets bit 6 of byte 1 in the FORMAT UNIT cdb.
296 -S, --security
298 sets the "Security Initialization" (SI) bit in the FORMAT UNIT
299 command's initialization pattern descriptor within the parameter
300 list. According to SBC-3 the default initialization pattern
301 "shall be written using a security erasure write technique". See
302 the NOTES section on the SCSI SANITIZE command. If this option
303 is given then the --ip_def option cannot be given.
304 -6, --six
306 Use 6 byte variants of MODE SENSE and MODE SELECT. The default
307 action is to use the 10 byte variants. Some MO drives need this
308 option set when doing a format.
309 -s, --size=LB_SZ
311 where LB_SZ is the logical block size (i.e. number of user bytes
312 in each block) to format the device to. The default value is
313 whatever is currently reported by the block descriptor in a MODE
314 SENSE command. If the block size given by this option is differ‐
315 ent from the current value then a MODE SELECT command is used to
316 change it prior to the FORMAT UNIT command being started (as
317 recommended in the SBC standards). Some SCSI disks have 512 byte
318 logical blocks by default and allow an alternate logical block
319 size of 4096 bytes. If the given size in unacceptable to the
320 disk, most likely an "Invalid field in parameter list" message
321 will appear in sense data (requires the use of '-v' to decode
322 sense data).
323 Note that formatting a disk to add or remove protection informa‐
324 tion is not regarded as a change to its logical block size so
325 this option should not be used.
326 -T, --tape=FM
328 will send a FORMAT MEDIUM command to the DEVICE with its FORMAT
329 field set to FM. This option is used to prepare a tape (i.e. the
330 "medium") in a tape drive for use. Values for FM include 0 to do
331 the "default" format; 1 to partition a volume and 2 to do a de‐
332 fault format then partition.
333 -m, --timeout=SECS
335 where SECS is the FORMAT UNIT, FORMAT WITH PRESET or FORMAT
336 MEDIUM command timeout in seconds. SECS will only be used if it
337 exceeds the internal timeout which is 20 seconds if the IMMED
338 bit is set and 72000 seconds (20 hours) or higher if the IMMED
339 bit is not set. If the disk size exceeds 4 TB then the timeout
340 value is increased to 144000 seconds (40 hours). And if it is
341 greater than 8 TB then the timeout value is increased to 288000
342 seconds (80 hours). If the timeout is exceeded then the operat‐
343 ing system will typically abort the command. Aborting a command
344 may escalate to a LUN reset (or worse). A timeout may also leave
345 the disk or tape format operation incomplete. And that may re‐
346 sult in the disk or tape being in a "format corrupt" state re‐
347 quiring another format to remedy the situation. So for various
348 reasons command timeouts are best avoided.
349 -v, --verbose
351 increase the level of verbosity, (i.e. debug output). "-vvv"
352 gives a lot more debug output.
353 -y, --verify
355 set the VERIFY bit in the FORMAT MEDIUM cdb. The default is that
356 the VERIFY bit is clear. This option is only appropriate for
357 tapes.
358 -V, --version
360 print the version string and then exit.
361 -w, --wait
363 the default format action is to set the "IMMED" bit in the FOR‐
364 MAT UNIT command's (short) parameter header. If this option
365 (i.e. --wait) is given then the "IMMED" bit is not set. If
366 --wait is given then the FORMAT UNIT, FORMAT WITH PRESET or FOR‐
367 MAT MEDIUM command waits until the format operation completes
368 before returning its response. This can be many hours on large
369 disks. See the --timeout=SECS option.
370 Alternatively this option may be useful when used together with
371 --ffmt=FFMT (and FFMT greater than 0) since the fast format may
372 only be a matter of seconds.
373
375 The SBC-3 draft (revision 20) defines PLIST, CLIST, DLIST and GLIST in
376 section 4.10 on "Medium defects". Briefly, the PLIST is the "primary"
377 list of manufacturer detected defects, the CLIST ("certification" list)
378 contains those detected during the format operation, the DLIST is a
379 list of defects that can be given to the format operation. The GLIST is
380 the grown list which starts in the format process as CLIST+DLIST and
381 can "grow" later due to automatic reallocation (see the ARRE and AWRE
382 bits in the Read-Write Error Recovery mode page (see sdparm(8))) and
383 use of the SCSI REASSIGN BLOCKS command (see sg_reassign(8)).
384 By the SBC-3 standard (following draft revision 36) the CLIST and DLIST
386 had been removed, leaving PLIST and GLIST. Only PLIST and GLIST are
387 found in the SBC-4 drafts.
388 The CMPLST bit (controlled by the --cmplst=0|1 option) determines
390 whether the existing GLIST, when the format operation is invoked, is
391 taken into account. The sg_format utility sets the FOV bit to zero
392 which causes DPRY=0, so the PLIST is taken into account, and DCRT=0, so
393 the CLIST is generated and used during the format process.
394 The sg_format utility does not permit a user to provide a defect list
396 (i.e. DLIST).
397
399 Protection Information (PI) is additional information held with logical
400 blocks so that an application and/or host bus adapter can check the
401 correctness of those logical blocks. PI is placed in one or more pro‐
402 tection intervals interleaved in each logical block. Each protection
403 interval follows the user data to which it refers. A protection inter‐
404 val contains 8 bytes made up of a 2 byte "logical block guard" (CRC), a
405 2 byte "logical block application guard", and a 4 byte "logical block
406 reference tag". Devices with 512 byte logical block size typically have
407 one protection interval appended, making its logical block data 520
408 bytes long. Devices with 4096 byte logical block size often have 8 pro‐
409 tection intervals spread across its logical block data for a total size
410 of 4160 bytes. Note that for all other purposes the logical block size
411 is considered to be 512 and 4096 bytes respectively.
412 The SBC-3 standard have added several "protection types" to the PI in‐
414 troduced in the SBC-2 standard. SBC-3 defines 4 protection types (types
415 0 to 3) with protection type 0 meaning no PI is maintained. While a de‐
416 vice may support one or more protection types, it can only be formatted
417 with 1 of the 4. To change a device's protection type, it must be
418 re-formatted. For more information see the Protection Information in
419 section 4.21 of draft SBC-4 revision 16.
420 A device that supports PI information (i.e. supports one or more pro‐
422 tection types 1, 2 and 3) sets the "PROTECT" bit in its standard IN‐
423 QUIRY response. It also sets the SPT field in the EXTENDED INQUIRY VPD
424 page response to indicate which protection types it supports. Given
425 PROTECT=1 then SPT=0 implies the device supports PI type 1 only, SPT=1
426 implies the device supports PI types 1 and 2, and various other non-ob‐
427 vious mappings up to SPT=7 which implies protection types 1, 2 and 3
428 are supported. The current protection type of a disk can be found in
429 the "P_TYPE" and "PROT_EN" fields in the response of a READ CAPACITY
430 (16) command (e.g. with the 'sg_readcap --long' utility).
431 Given that a device supports a particular protection type, a user can
433 then choose to format that disk with that protection type by setting
434 the "FMTPINFO" and "Protection Field Usage" fields in the FORMAT UNIT
435 command. Those fields correspond to the --fmtpinfo=FPI and the
436 --pfu=PFU options in this utility. The list below shows the four pro‐
437 tection types followed by the options of this utility needed to select
438 them:
439 0 : --fmtpinfo=0 --pfu=0
440 1 : --fmtpinfo=2 --pfu=0
441 2 : --fmtpinfo=3 --pfu=0
442 3 : --fmtpinfo=3 --pfu=1
443 The default value of FPI (in --fmtpinfo=FPI) is 0 and the default value
444 of PFU (in --pfu=PFU) is 0. So if neither --fmtpinfo=FPI nor --pfu=PFU
445 are given then protection type 0 (i.e. no protection information) is
446 chosen.
447
449 After a format that changes the logical block size or the number of
450 logical blocks on a disk, the operating system may need to be told to
451 re-initialize its setting for that disk. In Linux that can be done
452 with:
453 echo 1 > /sys/block/sd{letter(s)}/device/rescan
454 where "letter(s)" will be between 'a' and 'zzz'. The lsscsi utility in
455 Linux can be used to check the various namings of a disk.
456 The SBC-2 standard states that the REQUEST SENSE command should be used
458 for obtaining progress indication when the format command is underway.
459 However, tests on a selection of disks shows that TEST UNIT READY com‐
460 mands yield progress indications (but not REQUEST SENSE commands). So
461 the current version of this utility defaults to using TEST UNIT READY
462 commands to poll the disk to find out the progress of the format. The
463 --poll=PT option has been added to control this.
464 When the --format, --preset=ID or --tape=FM option is given without the
466 --wait option then the corresponding SCSI command is issued with the
467 IMMED bit set which causes the SCSI command to return after it has
468 started the format operation. The --early option will cause sg_format
469 to exit at that point. Otherwise the DEVICE is polled every 60 seconds
470 or every 10 seconds if FFMT is non-zero. The poll is with TEST UNIT
471 READY or REQUEST SENSE commands until one reports an "all clear" (i.e.
472 the format operation has completed). Normally these polling commands
473 will result in a progress indicator (expressed as a percentage) being
474 output to the screen. If the user gets bored watching the progress re‐
475 port then sg_format process can be terminated (e.g. with control-C)
476 without affecting the format operation which continues. However a tar‐
477 get or device reset (or a power cycle) will probably cause the format
478 to cease and the DEVICE to become "format corrupt".
479 When the --format (--preset=ID or --tape) and --wait options are both
481 given then this utility may take a long time to return. In this case
482 care should be taken not to send any other SCSI commands to the disk as
483 it may not respond leaving those commands queued behind the active for‐
484 mat command. This may cause a timeout in the OS driver (in a lot
485 shorter period than 20 hours applicable to some format operations).
486 This may result in the OS resetting the disk leaving the format opera‐
487 tion incomplete. This may leave the disk in a "format corrupt" state
488 requiring another format to remedy the situation. Modern SCSI devices
489 should yield a "not ready" sense key with an additional sense indicat‐
490 ing a format is in progress. With older devices the user should take
491 precautions that nothing attempts to access a device while it is being
492 formatted. Unmounting in mounted file systems on a DEVICE prior to
493 calling this utility is strongly advised.
494 When the block size (i.e. the number of bytes in each block) is changed
496 on a disk two SCSI commands must be sent: a MODE SELECT to change the
497 block size followed by a FORMAT command. If the MODE SELECT command
498 succeeds and the FORMAT fails then the disk may be in a state that the
499 standard calls "format corrupt". A block descriptor in a subsequent
500 MODE SENSE will report the requested new block size while a READ CAPAC‐
501 ITY command will report the existing (i.e. previous) block size. Alter‐
502 natively the READ CAPACITY command may fail, reporting the device is
503 not ready, potentially requiring a format. The solution to this situa‐
504 tion is to do a format again (and this time the new block size does not
505 have to be given) or change the block size back to the original size.
506 The SBC-2 standard states that the block count can be set back to the
508 manufacturer's maximum recommended value in a format or resize opera‐
509 tion. This can be done by placing an address of 0xffffffff (or the 64
510 bit equivalent) in the appropriate block descriptor field to a MODE SE‐
511 LECT command. In signed (two's complement) arithmetic that value corre‐
512 sponds to '-1'. So a --count=-1 causes the block count to be set back
513 to the manufacturer's maximum recommended value. To see exactly which
514 SCSI commands are being executed and parameters passed add the "-vvv"
515 option to the sg_format command line.
516 The FMTDATA field shown in the FORMAT UNIT cdb does not have a corre‐
518 sponding option in this utility. When set in the cdb it indicates an
519 additional parameter list will be sent to the DEVICE along with the
520 cdb. It is set as required, basically when any field in the parameter
521 list header is set.
522 Short stroking is a technique to trade off capacity for performance on
524 hard disks. "Hard" disk is often used to mean a storage device with
525 spinning platters which contain the user data. Solid State Disk (SSD)
526 is the newer form of storage device that contains no moving parts. Hard
527 disk performance is usually highest on the outer tracks (usually the
528 lower logical block addresses) so by resizing or reformatting a disk to
529 a smaller capacity, average performance will usually be increased.
530 Other utilities may be useful in finding information associated with
532 formatting. These include sg_inq(8) to fetch standard INQUIRY informa‐
533 tion (e.g. the PROTECT bit) and to fetch the EXTENDED INQUIRY VPD page
534 (e.g. RTO and GRD_CHK bits). The sdparm(8) utility can be used to ac‐
535 cess and potentially change the now obsolete format mode page.
536 scsiformat is another utility available for formatting SCSI disks with
538 Linux. It dates from 1997 (most recent update) and may be useful for
539 disks whose firmware is of that vintage.
540 The COUNT numeric argument may include a multiplicative suffix or be
542 given in hexadecimal. See the "NUMERIC ARGUMENTS" section in the
543 sg3_utils(8) man page.
544 The SCSI SANITIZE command was introduced in SBC-3 revision 27. It is
546 closely related to the ATA sanitize disk feature set and can be used to
547 remove all existing data from a disk. Sanitize is more likely to be im‐
548 plemented on modern disks (including SSDs) than FORMAT UNIT's security
549 initialization feature (see the --security option) and in some cases
550 much faster.
551 SSDs that support thin provisioning will typically unmap all logical
553 blocks during a format. The reason is to improve the SSD's endurance.
554 Also thin provisioned formats typically complete faster than fully pro‐
555 visioned ones on the same disk (see the --ip_def option). In either
556 case format operations on SSDs tend to be a lot faster than they are on
557 hard disks with spinning media.
558
560 Tape system use a variant of the FORMAT UNIT command used on disks.
561 Tape systems use the FORMAT MEDIUM command which is simpler with only
562 three fields in the cdb typically used. Apart from sharing the same op‐
563 code the cdbs of FORMAT UNIT and FORMAT MEDIUM are quite different.
564 FORMAT MEDIUM's fields are VERIFY, IMMED and FORMAT (with TRANSFER
565 LENGTH always set to 0). The VERIFY bit field is set with the --verify
566 option. The IMMED bit is manipulated by the --wait option in the same
567 way it is for disks; one difference is that if the --poll=PT option is
568 not given then it defaults to PT of 1 which means the poll is done with
569 REQUEST SENSE commands.
570 The argument given to the --tape=FM option is used to set the FORMAT
572 field. FM can take values from "-1" to "15" where "-1" (the default)
573 means don't do a tape format; value "8" to "15" are for vendor specific
574 formats. The --early option may also be used to set the IMMED bit and
575 then exit this utility (rather than poll periodically until it is fin‐
576 ished). In this case the tape drive will still be busy doing the format
577 for some time but, according to T10, should still respond in full to
578 the INQUIRY and REPORT LUNS commands. Other commands (including REQUEST
579 SENSE) should yield a "not ready" sense key with an additional sense
580 code of "Logical unit not ready, format in progress". Additionally RE‐
581 QUEST SENSE should contain a progress indication in its sense data.
582 When FM is 1 or 2 then the settings in the Medium partition mode page
584 control the partitioning. That mode page can be viewed and modified
585 with the sdparm utility.
586 Prior to invoking this utility the tape may need to be positioned to
588 the beginning of partition 0. In Linux that can typically be done with
589 the mt utility (e.g. 'mt -f /dev/st0 rewind').
590
592 These examples use Linux device names. For suitable device names in
593 other supported Operating Systems see the sg3_utils(8) man page.
594 In the first example below simply find out the existing block count and
596 size derived from two sources: a block descriptor in a MODE SELECT com‐
597 mand response and from the response of a READ CAPACITY commands. No
598 changes are made:
599 # sg_format /dev/sdm
601 Now a simple format, leaving the block count and size as they were pre‐
603 viously. The FORMAT UNIT command is executed in IMMED mode and the de‐
604 vice is polled every 60 seconds to print out a progress indication:
605 # sg_format --format /dev/sdm
607 Now the same format, but waiting (passively) until the format operation
609 is complete:
610 # sg_format --format --wait /dev/sdm
612 Next is a format in which the block size is changed to 520 bytes and
614 the block count is set to the manufacturer's maximum value (for that
615 block size). Note, not all disks support changing the block size:
616 # sg_format --format --size=520 /dev/sdm
618 Now a resize operation so that only the first 0x10000 (65536) blocks on
620 a disk are accessible. The remaining blocks remain unaltered.
621 # sg_format --resize --count=0x10000 /dev/sdm
623 Now resize the disk back to its normal (maximum) block count:
625 # sg_format --resize --count=-1 /dev/sdm
627 One reason to format a SCSI disk is to add protection information.
629 First check which protection types are supported by a disk (by checking
630 the SPT field in the Extended inquiry VPD page together with the Pro‐
631 tect bit in the standard inquiry response):
632 # sg_vpd -p ei -l /dev/sdb
634 extended INQUIRY data VPD page:
635 ACTIVATE_MICROCODE=0
636 SPT=1 [protection types 1 and 2 supported]
637 ....
638 Format with type 1 protection:
640 # sg_format --format --fmtpinfo=2 /dev/sdm
642 After a successful format with type 1 protection, READ CAPACITY(16)
644 should show something like this:
645 # sg_readcap -l /dev/sdm
647 Read Capacity results:
648 Protection: prot_en=1, p_type=0, p_i_exponent=0 [type 1 protec‐
649 tion]
650 Logical block provisioning: lbpme=0, lbprz=0
651 ....
652 To format with type 3 protection:
654 # sg_format --format --fmtpinfo=3 --pfu=1 /dev/sdm
656 For the disk shown above this will probably fail because the Extended
658 inquiry VPD page showed only types 1 and 2 protection are supported.
659 Here are examples of using fast format (FFMT field in FORMAT UNIT cdb)
661 to quickly switch between 512 and 4096 byte logical block size. Assume
662 disk starts with 4096 byte logical block size and all important data
663 has been backed up.
664 # sg_format --format --ffmt=1 --size=512 /dev/sdd
666 Now /dev/sdd should have 512 byte logical block size. And to switch it
668 back:
669 # sg_format --format --ffmt=1 --size=4096 /dev/sdd
671 Since fast formats can be very quick (a matter of seconds) using the
673 --wait option may be appropriate.
674 And to use the Format with preset command this invocation could be
676 used:
677 # sg_format --preset=1 --fmtmaxlba /dev/sdd
679 The FORMAT PRESETS VPD page (0xb8) should be consulted to check that
681 Preset identifier 0x1 is there and has the expected format (i.e. "de‐
682 fault host aware zoned block device model with 512 bytes of user data
683 in each logical block"). That VPD page can be viewed with the sg_vpd
684 utility.
685
687 The exit status of sg_format is 0 when it is successful. Otherwise see
688 the sg3_utils(8) man page. Unless the --wait option is given, the exit
689 status may not reflect the success of otherwise of the format. Using
690 sg_turs(8) and sg_readcap(8) after the format operation may be wise.
691 The Unix convention is that "no news is good news" but that can be a
693 bit unnerving after an operation like format, especially if it finishes
694 quickly (i.e. before the first progress poll is sent). Giving the
695 --verbose option once should supply enough additional output to settle
696 those nerves.
697
699 Written by Grant Grundler, James Bottomley and Douglas Gilbert.
700
702 Report bugs to <dgilbert at interlog dot com>.
703
705 Copyright © 2005-2020 Grant Grundler, James Bottomley and Douglas
706 Gilbert
707 This software is distributed under the GPL version 2. There is NO war‐
708 ranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR‐
709 POSE.
710
712 sg_turs(8), sg_requests(8), sg_inq(8), sg_modes(8), sg_vpd(8), sg_reas‐
713 sign(8), sg_readcap(8), sg3_utils(8), sg_sanitize(8) [all in
714 sg3_utils], lsscsi(8), mt(mt-st), sdparm(8), scsiformat (old), hd‐
715 parm(8)
716sg3_utils-1.45 January 2020 SG_FORMAT(8)