1SG_FORMAT(8) SG3_UTILS SG_FORMAT(8)
2
6 sg_format - format or resize a SCSI disk (perhaps change its block
7 size)
8
10 sg_format [--cmplst={0|1}] [--count=COUNT] [--dcrt] [--early] [--fmt‐
11 pinfo=FPI] [--format] [--help] [--long] [--pfu=PFU] [--pie=PIE]
12 [--pinfo] [--poll=PT] [--resize] [--rto_req] [--security] [--six]
13 [--size=SIZE] [--verbose] [--version] [--wait] DEVICE
14
16 Not all SCSI direct access devices need to be formatted and some have
17 vendor specific formatting procedures. SCSI disks with rotating media
18 are probably the largest group that do support a 'standard' format
19 operation. They are typically factory formatted to a block size of 512
20 bytes with the largest number of blocks that the manufacturer recom‐
21 mends. The manufacturer's recommendation typically leaves aside a cer‐
22 tain number of tracks, spread across the media, for reassignment of
23 blocks to logical block addresses during the life of the disk.
24 This utility can format modern SCSI disks and potentially change their
26 block size (if permitted) and the block count (i.e. number of accessi‐
27 ble blocks on the media also known as "resizing"). Resizing a disk to
28 less than the manufacturer's recommended block count is sometimes
29 called "short stroking" (see NOTES section). Resizing the block count
30 while not changing the block size may not require a format operation.
31 The SBC-2 standard (see www.t10.org) has obsoleted the "format device"
32 mode page. Many of the low level details found in that mode page are
33 now left up to the discretion of the manufacturer.
34 When this utility is used without options (i.e. it is only given a
36 DEVICE argument) it prints out the existing block size and block count
37 derived from two sources. These two sources are a block descriptor in
38 the response to a MODE SENSE command and the response to a READ CAPAC‐
39 ITY command. The reason for this double check is to detect a "format
40 corrupt" state (see NOTES section). This usage will not modify the
41 disk.
42 When this utility is used with the "--format" (or "-F") option it will
44 attempt to format the given DEVICE. There is a 10 second pause during
45 which time the user is invited twice (5 seconds apart) to abort sg_for‐
46 mat. This occurs just prior the SCSI FORMAT UNIT command being issued.
47 See the NOTES section for more information.
48 Protection information is optional and is made up of 8 additional bytes
50 associated with each logical block. Four protection types are defined
51 with protection type 0 being no additional protection bytes. See the
52 PROTECTION TYPES section below for more information.
53
55 Arguments to long options are mandatory for short options as well. The
56 options are arranged in alphabetical order based on the long option
57 name.
58 -C, --cmplst={0|1}
60 sets the CMPLST ("complete list") bit in the FORMAT UNIT cdb to
61 0 or 1. The default is 1 in which case the existing GLIST
62 (grown list) is ignored. If the value is 0 then the existing
63 GLIST is taken into account. See the LISTS section below. In
64 most cases this bit should be left set; some MO disk drives need
65 this bit cleared.
66 -c, --count=COUNT
68 where COUNT is the number of blocks to be formatted or media to
69 be resized to. Can be used with either --format or --resize.
70 With --format this option need not be given in which case it is
71 assumed to be zero. With --format the interpretation of COUNT
72 is:
73 (COUNT > 0) : only format the first COUNT blocks and READ
74 CAPACITY will report COUNT blocks after format
75 (COUNT = 0) and block size unchanged : use existing block
76 count
77 (COUNT = 0) and block size changed : recommended maximum block
78 count for new block size
79 (COUNT = -1) : use recommended maximum block count
80 (COUNT < -1) : illegal
81 With --resize this option must be given and COUNT has this
82 interpretation:
83 (COUNT > 0) : after resize READ CAPACITY will report COUNT
84 blocks
85 (COUNT = 0) : after resize READ CAPACITY will report 0 blocks
86 (COUNT = -1) : after resize READ CAPACITY will report its
87 maximum number of blocks
88 (COUNT < -1) : illegal
89 In both cases if the given COUNT exceeds the maximum number of
90 blocks (for the block size) then the disk reports an error. See
91 NOTES section below.
92 -D, --dcrt
94 this option sets the DCRT bit in the FORMAT UNIT command's
95 parameter list header. It will "disable certification". Certifi‐
96 cation verifies that blocks are usable during the format
97 process. Using this option may speed the format. The default
98 action of this utility (i.e. when this option is not given) is
99 to clear the DCRT bit thereby requesting "media certification".
100 When the DCRT bit is set, the FOV bit must also be set hence
101 sg_format does that.
102 -e, --early
104 during a format operation, The default action of this utility is
105 to poll the disk every 60 seconds to determine the progress of
106 the format operation until it is finished. When this option is
107 given this utility will exit "early", that is as soon as the
108 format operation has commenced. Then the user can monitor the
109 progress of the ongoing format operation with other utilities
110 (e.g. sg_turs(8) or sg_requests(8)). This option and --wait are
111 mutually exclusive.
112 -f, --fmtpinfo=FPI
114 sets the FMTPINFO field in the FORMAT UNIT cdb to a value
115 between 0 and 3. The default value is 0. The FMTPINFO field
116 from SBC-3 revision 16 is a 2 bit field (bits 7 and 6 of byte 1
117 in the cdb). Prior to that it was a single bit field (bit 7 of
118 byte 1 in the cdb) and there was an accompanying bit called
119 RTO_REQ (bit 6 of byte 1 in the cdb). The deprecated options
120 "--pinfo" and "--rto-req" represent the older usage. This option
121 should be used in their place. See the PROTECTION TYPES section
122 below for more information.
123 -F, --format
125 issue a SCSI FORMAT UNIT command. This will destroy all the
126 data held on the media. This option is required to change the
127 block size of a disk. The user is given a 10 second count down
128 to ponder the wisdom of doing this, during which time control-C
129 (amongst other Unix commands) can be used to kill this process
130 before it does any damage. See NOTES section for implementation
131 details and EXAMPLES section for typical use.
132 -h, --help
134 print out the usage information then exit.
135 -l, --long
137 the default action of this utility is to assume 32 bit logical
138 block addresses. With 512 byte block size this permits more than
139 2 terabytes (almost 2 ** 41 bytes) on a single disk. This option
140 selects commands and parameters that allow for 64 bit logical
141 block addresses. Specifically this option sets the "longlba"
142 flag in the MODE SENSE (10) command and uses READ CAPACITY (16)
143 rather than READ CAPACITY (10). If this option is not given and
144 READ CAPACITY (10) or MODE SELECT detects a disk the needs more
145 than 32 bits to represent its logical blocks then it is set
146 internally. This option does not set the LONGLIST bit in the
147 FORMAT UNIT command. The LONGLIST bit is set as required depend‐
148 ing other parameters (e.g. when '--pie=PIE' is greater than
149 zero).
150 -P, --pfu=PFU
152 sets the "Protection Field Usage" field in the parameter block
153 associated with a FORMAT UNIT command to PFU. The default value
154 is 0, the only other defined value currently is 1. See the PRO‐
155 TECTION TYPES section below for more information.
156 -q, --pie=PIE
158 sets the "Protection Interval Exponent" field in the parameter
159 block associated with a FORMAT UNIT command to PIE. The default
160 value is 0. This field first appeared in SBC-3 revision 18.
161 -p, --pinfo
163 this option is deprecated, use the --fmtpinfo=FPI option
164 instead. If used, then it sets bit 7 of byte 1 in the FORMAT
165 UNIT cdb and that is equivalent to setting --fmtpinfo=2. [So if
166 --pinfo is used (plus --fmtpinfo=FPI and --pfu=PFU are not given
167 or their arguments are 0) then protection type 1 is selected.]
168 -x, --poll=PT
170 where PT is the type of poll used. If PT is 0 then a TEST UNIT
171 READY command is used, otherwise a REQUEST SENSE command is
172 used. The default is currently 0 but this will change to 1 in
173 the near future. See the NOTES sections below.
174 -r, --resize
176 rather than format the disk, it can be resized. This means
177 changing the number of blocks on the device reported by the READ
178 CAPACITY command. This option should be used with the
179 --count=COUNT option. The contents of all logical blocks on the
180 media remain unchanged when this option is used. This means that
181 any resize operation can be reversed. This option cannot be used
182 together with either --format or a --size=SIZE whose argument is
183 different to the existing block size.
184 -R, --rto_req
186 The option is deprecated, use the --fmtpinfo=FPI option instead.
187 If used, then it sets bit 6 of byte 1 in the FORMAT UNIT cdb.
188 -S, --security
190 sets the "Security Initialization" (SI) bit in the FORMAT UNIT
191 command's initialization pattern descriptor within the parameter
192 list. According to SBC-3 the default initialization pattern
193 "shall be written using a security erasure write technique". See
194 the NOTES section on the SCSI SANITIZE command.
195 -6, --six
197 Use 6 byte variants of MODE SENSE and MODE SELECT. The default
198 action is to use the 10 byte variants. Some MO drives need this
199 option set when doing a format.
200 -s, --size=SIZE
202 where SIZE is the block size (i.e. number of bytes in each
203 block) to format the device to. The default value is whatever is
204 currently reported by the block descriptor in a MODE SENSE com‐
205 mand. If the block size given by this option is different from
206 the current value then a MODE SELECT command is used to change
207 it prior to the FORMAT UNIT command being started (as recom‐
208 mended in the draft standard). Many SCSI disks have 512 byte
209 sectors by default and allow up to 16 bytes extra in a sector
210 (i.e. 528 byte sectors). If the given size in unacceptable with
211 the disk, most likely an "Invalid field in parameter list" mes‐
212 sage will appear in sense data (requires the use of '-v' to
213 decode sense data).
214 -v, --verbose
216 increase the level of verbosity, (i.e. debug output). "-vvv"
217 gives a lot more debug output.
218 -V, --version
220 print the version string and then exit.
221 -w, --wait
223 the default format action is to set the "IMMED" bit in the FOR‐
224 MAT UNIT command's (short) parameter header. If this option
225 (i.e. --wait) is given then the "IMMED" bit is not set. If
226 --wait is given the FORMAT UNIT command waits until the format
227 operation completes before returning its response. This can be
228 many hours on large disks. This utility sets a 15 hour timeout
229 on such a FORMAT UNIT command!
230
232 The SBC-3 draft (revision 29) defines PLIST, CLIST, DLIST and GLIST in
233 section 4.13 on "Medium defects". Briefly, the PLIST is the "primary"
234 list of manufacturer detected defects, the CLIST ("certification" list)
235 contains those detected during the format operation, the DLIST is a
236 list of defects that can be given to the format operation. The GLIST is
237 the grown list which starts in the format process as CLIST+DLIST and
238 can "grow" later due to automatic reallocation (see the ARRE and AWRE
239 bits in the read-write error recovery mode page (see sdparm(8))) and
240 use of the SCSI REASSIGN BLOCKS command (see sg_reassign(8)).
241 The CMPLST bit (controlled by the --cmplst=0|1 option) determines
243 whether the existing GLIST, when the format operation is invoked, is
244 taken into account. The sg_format utility sets the FOV bit to zero
245 which causes DPRY=0, so the PLIST is taken into account, and DCRT=0, so
246 the CLIST is generated and used during the format process.
247 The sg_format utility does not permit a user to provide a defect list
249 (i.e. DLIST).
250
252 SBC-3 drafts have added several "protection types" to the "protection
253 information" introduced in the SBC-2 standard. See the "protection
254 information" section (section 4.21 in draft SBC-3 rev 29). 8 bytes of
255 protection information are added to each logical block (a 2 byte "logi‐
256 cal block guard" (CRC), a 2 byte "logical block application guard", and
257 a 4 byte "logical block reference tag"). SBC-3 defines 4 protection
258 types (types 0 to 3) with protection type 0 meaning no protection
259 information is maintained.
260 A device that supports protection information (i.e. supports one or
262 more protection types of 1 or higher) sets the "PROTECT" bit in its
263 standard INQUIRY response. It also sets the SPT field in the EXTENDED
264 INQUIRY VPD page response to indicate which protection types it sup‐
265 ports. The current protection type of a disk can be found in the
266 "P_TYPE" and "PROT_EN" fields in the response of a READ CAPACITY (16)
267 command (e.g. with the 'sg_readcap --long' utility).
268 Given that a device supports a particular protection type, a user can
270 then choose to format that disk with that protection type by setting
271 the "FMTPINFO" and "Protection Field Usage" fields in the FORMAT UNIT
272 command. Those fields correspond to the --fmtpinfo=FPI and the
273 --pfu=PFU options in this utility. The list below shows the four pro‐
274 tection types followed by the options of this utility needed to select
275 them:
276 0 : --fmtpinfo=0 --pfu=0
277 1 : --fmtpinfo=2 --pfu=0
278 2 : --fmtpinfo=3 --pfu=0
279 3 : --fmtpinfo=3 --pfu=1
280 The default value of FPI (in --fmtpinfo=FPI) is 0 and the default value
281 of PFU (in --pfu=PFU) is 0. So if neither --fmtpinfo=FPI nor --pfu=PFU
282 are given then protection type 0 (i.e. no protection information) is
283 chosen.
284
286 The SBC-2 standard states that the REQUEST SENSE command should be used
287 for obtaining progress indication when the format command is underway.
288 However, tests on a selection of disks shows that TEST UNIT READY com‐
289 mands yield progress indications (but not REQUEST SENSE commands). So
290 the current version of this utility defaults to using TEST UNIT READY
291 commands to poll the disk to find out the progress of the format. The
292 --poll=PT option has been added to control this.
293 When the --format option is given without the --wait option then the
295 SCSI FORMAT UNIT command is issued with the IMMED bit set which causes
296 the SCSI command to return after it has started the format operation.
297 The --early option will cause sg_format to exit at that point. Other‐
298 wise the DEVICE is polled every 60 seconds with TEST UNIT READY or
299 REQUEST SENSE commands until it reports an "all clear" (i.e. the format
300 operation has completed). Normally these polling commands will result
301 in a progress indicator (expressed as a percentage) being output to the
302 screen. If the user gets bored watching the progress report then
303 sg_format process can be terminated (e.g. with control-C) without
304 affecting the format operation which continues. However a target or
305 device reset (or a power cycle) will probably cause the device to
306 become "format corrupt".
307 When the --format and --wait options are both given then this utility
309 may take a long time to return. In this case care should be taken not
310 to send any other SCSI commands to the disk as it may not respond leav‐
311 ing those commands queued behind the active format command. This may
312 cause a timeout in the OS driver (in a lot shorter period than 15 hours
313 applicable to some format operations). This may result in the OS reset‐
314 ting the disk leaving the format operation incomplete. This may leave
315 the disk in a "format corrupt" state requiring another format to remedy
316 the situation.
317 When the block size (i.e. the number of bytes in each block) is changed
319 on a disk two SCSI commands must be sent: a MODE SELECT to change the
320 block size followed by a FORMAT command. If the MODE SELECT command
321 succeeds and the FORMAT fails then the disk may be in a state that the
322 draft standard calls "format corrupt". A block descriptor in a subse‐
323 quent MODE SENSE will report the requested new block size while a READ
324 CAPACITY command will report the existing (i.e. different) block size.
325 Alternatively the READ CAPACITY command may fail, reporting the device
326 is not ready, potentially requiring a format. The solution to this sit‐
327 uation is to do a format again (and this time the new block size does
328 not have to be given) or change the block size back to the original
329 size.
330 The SBC-2 standard states that the block count can be set back to the
332 manufacturer's maximum recommended value in a format or resize opera‐
333 tion. This can be done by placing an address of 0xffffffff (or the 64
334 bit equivalent) in the appropriate block descriptor field to a MODE
335 SELECT command. In signed (two's complement) arithmetic that value cor‐
336 responds to the manufacturer's maximum recommended value. To see
337 exactly which SCSI commands are being executed and parameters passed
338 add the "-vvv" option to the sg_format command line.
339 Short stroking is a technique to trade off capacity for performance.
341 Rotating disk performance is usually highest on the outer tracks (i.e.
342 lower logical block addresses) so by resizing or reformatting a disk to
343 a smaller capacity, average performance will usually be increased.
344 Other utilities may be useful in finding information associated with
346 formatting. These include sg_inq(8) to fetch standard INQUIRY informa‐
347 tion (e.g. the PROTECT bit) and to fetch the EXTENDED INQUIRY VPD page
348 (e.g. RTO and GRD_CHK bits). The sdparm(8) utility can be used to
349 access and potentially change the now obsolete format mode page.
350 scsiformat is another utility available for formatting SCSI disks with
352 Linux. It dates from 1997 (most recent update) and may be useful for
353 disks whose firmware is of that vintage.
354 The COUNT numeric argument may include a multiplicative suffix or be
356 given in hexadecimal. See the "NUMERIC ARGUMENTS" section in the
357 sg3_utils(8) man page.
358 The SCSI SANITIZE command was introduced in SBC-3 revision 27. It is
360 closely related to the ATA sanitize disk feature set and can be used to
361 remove all existing data from a disk. Sanitize is more likely to be
362 implemented on modern disks (including SSDs) than FORMAT UNIT's secu‐
363 rity initialization feature (see the --security option) and in some
364 cases much faster.
365
367 These examples use Linux device names. For suitable device names in
368 other supported Operating Systems see the sg3_utils(8) man page.
369 In the first example below simply find out the existing block count and
371 size derived from two sources: a block descriptor in a MODE SELECT com‐
372 mand response and from the response of a READ CAPACITY commands. No
373 changes are made:
374 # sg_format /dev/sdm
376 Now a simple format, leaving the block count and size as they were pre‐
378 viously. The FORMAT UNIT command is executed in IMMED mode and the
379 device is polled every 60 seconds to print out a progress indication:
380 # sg_format --format /dev/sdm
382 Now the same format, but waiting (passively) until the format operation
384 is complete:
385 # sg_format --format --wait /dev/sdm
387 Next is a format in which the block size is changed to 520 bytes and
389 the block count is set to the manufacturer's maximum value (for that
390 block size). Note, not all disks support changing the block size:
391 # sg_format --format --size=520 /dev/sdm
393 Now a resize operation so that only the first 0x10000 (65536) blocks on
395 a disk are accessible. The remaining blocks remain unaltered.
396 # sg_format --resize --count=0x10000 /dev/sdm
398 Now resize the disk back to its normal (maximum) block count:
400 # sg_format --resize --count=-1 /dev/sdm
402 One reason to format a SCSI disk is to add protection information.
404 First check which protection types are supported by a disk (by checking
405 the SPT field in the Extended inquiry VPD page together with the Pro‐
406 tect bit in the standard inquiry response):
407 # sg_vpd -p ei -l /dev/sdb
409 extended INQUIRY data VPD page:
410 ACTIVATE_MICROCODE=0
411 SPT=1 [protection types 1 and 2 supported]
412 ....
413 Format with type 1 protection:
415 # sg_format --format --fmtpinfo=2 /dev/sdm
417 After a successful format with type 1 protection, READ CAPACITY(16)
419 should show something like this:
420 # sg_readcap -l /dev/sdm
422 Read Capacity results:
423 Protection: prot_en=1, p_type=0, p_i_exponent=0 [type 1 protec‐
424 tion]
425 Logical block provisioning: lbpme=0, lbprz=0
426 ....
427 To format with type 3 protection:
429 # sg_format --format --fmtpinfo=3 --pfu=1 /dev/sdm
431 For the disk shown above this will probably fail because the Extended
433 inquiry VPD page showed only types 1 and 2 protection are supported.
434
436 The exit status of sg_format is 0 when it is successful. Otherwise see
437 the sg3_utils(8) man page. Unless the --wait option is given, the exit
438 status may not reflect the success of otherwise of the format. Using
439 sg_turs(8) and sg_readcap(8) after the format operation may be wise.
440
442 Written by Grant Grundler, James Bottomley and Douglas Gilbert.
443
445 Report bugs to <dgilbert at interlog dot com>.
446
448 Copyright © 2005-2013 Grant Grundler, James Bottomley and Douglas
449 Gilbert
450 This software is distributed under the GPL version 2. There is NO war‐
451 ranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR‐
452 POSE.
453
455 sg_turs(8), sg_requests(8), sg_inq(8), sg_modes(8), sg_vpd(8), sg_reas‐
456 sign(8), sg_readcap(8), sg3_utils(8), sg_sanitize(8) [all in
457 sg3_utils], sdparm(8), scsiformat (old), hdparm(8)
458sg3_utils-1.37 June 2013 SG_FORMAT(8)