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] [--resize] [--rto_req] [--security] [--six] [--size=SIZE]
13 [--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 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 (apart from a DEVICE) it
36 prints out the existing block size and block count derived from two
37 sources. These two sources are a block descriptor in the response to a
38 MODE SENSE command and the response to a READ CAPACITY command. The
39 reason for this double check is to detect a "format corrupt" state (see
40 NOTES section). This usage will not modify the disk.
41 When this utility is used with the "--format" (or "-F") option it will
43 attempt to format the given DEVICE. There is a 10 second pause during
44 which time the user is invited (twice 5 seconds apart) to abort sg_for‐
45 mat. This occurs just prior the SCSI FORMAT UNIT command being issued.
46 See the NOTES section for more information.
47 Recent SBC-3 drafts add several "protection types" to the "protection
49 information" introduced in the SBC-2 standard. See the "protection
50 information" section (section 4.18 in draft SBC-3 rev 18). 8 bytes of
51 protection information are added to each block (a 2 byte "logical block
52 guard" (CRC), a 2 byte "logical block application guard", and a 4 byte
53 "logical block reference tag"). A device that supports protection
54 information sets the "PROTECT" bit in its standard INQUIRY response.
55 The "FMTPINFO" field in in the FORMAT UNIT command cdb plus the "Pro‐
56 tection Field Usage" in the parameter header are associated with pro‐
57 tection information and can be set by this utility.
58
60 Arguments to long options are mandatory for short options as well. The
61 options are arranged in alphabetical order based on the long option
62 name.
63 -C, --cmplst=0 | 1
65 sets the CMPLST ("complete list") bit in the FORMAT UNIT cdb to
66 0 or 1. The default is 1 in which case the existing GLIST
67 (grown list) is ignored. If the value is 0 then the existing
68 GLIST is taken into account. See the LISTS section below. Active
69 when the --format option is given. In most cases this bit should
70 be left set; some MO disk drives need this bit cleared. The SCSI
71 to ATA Translation (SAT) standard (prior draft: sat-r09)
72 requires this bit to be cleared.
73 -c, --count=COUNT
75 where COUNT is the number of blocks to be formatted or media to
76 be resized to. Can be used with either --format or --resize.
77 With --format this option need not be given in which case it is
78 assumed to be zero. With --format the interpretation of COUNT
79 is:
80 (COUNT > 0) : only format the first COUNT blocks and READ
81 CAPACITY will report COUNT blocks after format
82 (COUNT = 0) and block size unchanged : use existing block
83 count
84 (COUNT = 0) and block size changed : recommended maximum block
85 count for new block size
86 (COUNT = -1) : use recommended maximum block count
87 (COUNT < -1) : illegal
88 With --resize this option must be given and COUNT has this
89 interpretation:
90 (COUNT > 0) : after resize READ CAPACITY will report COUNT
91 blocks
92 (COUNT = 0) : after resize READ CAPACITY will report 0 blocks
93 (COUNT = -1) : after resize READ CAPACITY will report its
94 maximum number of blocks
95 (COUNT < -1) : illegal
96 In both cases if the given COUNT exceeds the maximum number of
97 blocks (for the block size) then the disk reports an error. See
98 NOTES section below.
99 -D, --dcrt
101 this option sets the DCRT bit in the FORMAT UNIT command's
102 parameter list header. It will "disable certification". Certifi‐
103 cation verifies that blocks are usable during the format
104 process. Using this option may speed the format. The default
105 action of this utility (i.e. when this option is not given) is
106 to clear the DCRT bit thereby requesting "media certification".
107 When the DCRT bit is set, the FOV bit must also be set hence
108 sg_format does that.
109 -e, --early
111 this option is active when --format is given. The default action
112 of this utility is to poll the disk every 30 seconds to deter‐
113 mine the progress of the format operation until it is finished.
114 When this option is given this utility will exit "early" as soon
115 as the format has commenced. Then the user can monitor the
116 progress of the ongoing format operation with other utilities
117 (e.g. sg_turs(8) or sg_requests(8)). This option and --wait can‐
118 not both be given.
119 -f, --fmtpinfo=FPI
121 sets the FMTPINFO field in the FORMAT UNIT cdb to a value
122 between 0 and 3. The default value is 0. The FMTPINFO field
123 from SBC-3 revision 16 is a 2 bit field (bits 7 and 6 of byte 1
124 in the cdb). Prior to that it was a single bit field (bit 7 of
125 byte 1 in the cdb) and there was an accompanying bit called
126 RTO_REQ (bit 6 of byte 1 in the cdb). The deprecated options
127 "--pinfo" and "--rto-req" represent the older usage. This option
128 should be used in their place. This option has no action unless
129 --format is given.
130 -F, --format
132 issue a SCSI FORMAT UNIT command. This will destroy all the
133 data held on the media. This option is required to change the
134 block size of a disk. The user is given a 10 second count down
135 to ponder the wisdom of doing this, during which time control-C
136 (amongst other Unix commands) can be used to kill this process
137 before it does any damage. See NOTES section for implementation
138 details and EXAMPLES section for typical use.
139 -h, --help
141 print out the usage information then exit.
142 -l, --long
144 the default action of this utility is to assume 32 bit logical
145 block addresses. With 512 byte block size this permits almost 2
146 terabytes (almost 2 ** 41 bytes) on a single disk. This option
147 selects commands and parameters that allow for 64 bit logical
148 block addresses. Specifically this option sets the "longlba"
149 flag in the MODE SENSE (10) command and uses READ CAPACITY (16)
150 rather than READ CAPACITY (10). This option does not set the
151 LONGLIST bit in the FORMAT UNIT command. The LONGLIST bit is set
152 as required depending other parameters (e.g. when '--pie=PIE' is
153 greater than zero).
154 -P, --pfu=PFU
156 sets the "Protection Field Usage" field in the parameter block
157 associated with a FORMAT UNIT command to PFU. The default value
158 is 0, the only other defined value currently is 1. Used together
159 with --fmtpinfo=FPI to specify the "protection type" to format
160 the disk to (see SBC-3).
161 -p, --pinfo
163 The option is deprecated, use the --fmtpinfo=FPI option instead.
164 If used, then it sets bit 7 of byte 1 in the FORMAT UNIT cdb.
165 Has no action unless --format is given.
166 -q, --pie=PIE
168 sets the "Protection Interval Exponent" field in the parameter
169 block associated with a FORMAT UNIT command to PIE. The default
170 value is 0. This field first appeared in SBC-3 revision 18. Has
171 no action unless --format is given.
172 -r, --resize
174 rather than format the disk, it can be resized. This means
175 changing the number of blocks on the device reported by the READ
176 CAPACITY command. This option should be used with the
177 --count=COUNT option. The contents of all logical blocks on the
178 media remain unchanged when this option is used. This means that
179 any resize operation can be reversed. This option cannot be used
180 together with either --format or a --size=SIZE whose argument is
181 different to the existing block size.
182 -R, --rto_req
184 The option is deprecated, use the --fmtpinfo=FPI option instead.
185 If used, then it sets bit 6 of byte 1 in the FORMAT UNIT cdb.
186 Has no action unless --format is given.
187 -S, --security
189 sets the "Security Initialization" (SI) bit in the FORMAT UNIT
190 command's initialization pattern descriptor within the parameter
191 list. According to SBC-3 the default initialization pattern
192 "shall be written using a security erasure write technique". The
193 SI bit is found in SBC (1998) and SBC-2 (2005) so vendors should
194 support it. SATA and parallel ATA disks have a separate command
195 called SECURITY ERASE UNIT to perform this action. Recent ver‐
196 sions of the hdparm utility can execute that ATA command.
197 -6, --six
199 Use 6 byte variants of MODE SENSE and MODE SELECT. The default
200 action is to use the 10 byte variants. Some MO drives need this
201 option set when doing a format.
202 -s, --size=SIZE
204 where SIZE is the block size (i.e. number of bytes in each
205 block) to format the device to. The default value is whatever
206 is currently reported by the block descriptor in a MODE SENSE
207 command. This option is only active when the --format option is
208 also given. If the block size given by this option is different
209 from the current value then a MODE SELECT command is used to
210 change it prior to the FORMAT UNIT command being started (as
211 recommended in the draft standard). Recent SCSI disks usually
212 have 512 byte sectors by default and allow up to 16 bytes extra
213 in a sector (i.e. 528 byte sectors). If the given size in unac‐
214 ceptable to the disk, most likely an "Invalid field in parameter
215 list" message will appear in sense data (requires the use of
216 '-v' to decode sense data).
217 -v, --verbose
219 increase the level of verbosity, (i.e. debug output). "-vvv"
220 gives the maximum debug output.
221 -V, --version
223 print the version string and then exit.
224 -w, --wait
226 this option only has an effect when used together with the
227 --format option. The default format action is to set the "IMMED"
228 bit in the FORMAT UNIT command's (short) parameter header. If
229 this option (i.e. --wait) is given then the "IMMED" bit is not
230 set. If --wait is given the FORMAT UNIT command waits until the
231 format operation completes before returning its response. This
232 can be several hours on large disks. This utility sets a four
233 hour timeout on such a FORMAT UNIT command.
234
236 The SBC-3 draft (revision 18) defines PLIST, CLIST, DLIST and GLIST in
237 section 4.10 on "Medium defects". Briefly, the PLIST is the "primary"
238 list of manufacturer detected defects, the CLIST ("certification" list)
239 contains those detected during the format operation, the DLIST is a
240 list of defects that can be given to the format operation. The GLIST is
241 the grown list which starts in the format process as CLIST+DLIST and
242 can "grow" later due to automatic reallocation (see the ARRE and AWRE
243 bits in the read-write error recovery mode page (see sdparm(8))) and
244 use of the SCSI REASSIGN BLOCKS command (see sg_reassign(8)).
245 The CMPLST bit (controlled by the --cmplst=0|1 option) determines
247 whether the existing GLIST, when the format operation is invoked, is
248 taken into account. The sg_format utility sets the FOV bit to zero
249 which causes DPRY=0, so the PLIST is taken into account, and DCRT=0, so
250 the CLIST is generated and used during the format process.
251 The sg_format utility does not permit a user to provide a defect list
253 (i.e. DLIST).
254
256 The SBC-2 standard states that the REQUEST SENSE command should be used
257 for obtaining a progress indication when the format command is under‐
258 way. However, tests on a selection of recent disks shows that TEST
259 UNIT READY commands yield progress indications (but not REQUEST SENSE
260 commands). So the current version of this utility uses TEST UNIT READY
261 commands to poll the disk to find out the progress of the format. A new
262 option may be required to handle this when disks catch up.
263 When the --format option is given without the --wait option then the
265 SCSI FORMAT UNIT command is issued with the IMMED bit set which causes
266 the SCSI command to return after it has started the format operation.
267 The --early option will cause sg_format to exit at that point. Other‐
268 wise the DEVICE is polled every 30 seconds with TEST UNIT READY com‐
269 mands until it reports an "all clear" (i.e. the format operation has
270 completed). Normally these polling commands will result in a progress
271 indicator (expressed as a percentage) being output to the screen. If
272 the user gets bored watching the progress report then sg_format process
273 can be terminated (e.g. with control-C) without affecting the format
274 operation which continues. However a bus or device reset (or a power
275 cycle) will probably cause the device to become "format corrupt".
276 When the --format and --wait options are both given then this utility
278 may take a long time to return. In this case care should be taken not
279 to send any other SCSI commands to the disk as it may not respond leav‐
280 ing those commands queued behind the active format command. This may
281 cause a timeout in the OS driver (in a lot shorter period than 4 hours
282 applicable to some format operations). This may result in the OS reset‐
283 ting the disk leaving the format operation incomplete. This may leave
284 the disk in a "format corrupt" state requiring another format to remedy
285 the situation.
286 When the block size (i.e. the number of bytes in each block) is changed
288 on a disk two SCSI commands must be sent: a MODE SELECT to change the
289 block size followed by a FORMAT command. If the MODE SELECT command
290 succeeds and the FORMAT fails then the disk may be in a state that the
291 draft standard calls "format corrupt". A block descriptor in a subse‐
292 quent MODE SENSE will report the requested new block size while a READ
293 CAPACITY command will report the existing (i.e. different) block size.
294 Alternatively the READ CAPACITY command may fail, reporting the device
295 is not ready, potentially requiring a format. The solution to this sit‐
296 uation is to do a format again (and this time the new block size does
297 not have to be given) or change the block size back to the original
298 size.
299 The SBC-2 standard states that the block count can be set back to the
301 manufacturer's maximum recommended value in a format or resize opera‐
302 tion. This can be done by placing an address of 0xffffffff (or the 64
303 bit equivalent) in the appropriate block descriptor field to a MODE
304 SELECT command. In signed (two's complement) arithmetic that value cor‐
305 responds to '-1'. So a --count=-1 causes the block count to be set back
306 to the manufacturer's maximum recommended value. To see exactly which
307 SCSI commands are being executed and parameters passed add "-vvv" to
308 the sg_format command line.
309 Short stroking is a technique to trade off capacity for performance.
311 Disk performance is usually highest on the outer tracks (i.e. lower
312 logical block addresses) so by resizing or reformatting a disk to a
313 smaller capacity, average performance will usually be increased.
314 Other utilities may be useful in finding information associated with
316 formatting. These include sg_inq(8) to fetch standard INQUIRY informa‐
317 tion (e.g. the PROTECT bit) and to fetch the extended INQUIRY VPD page
318 (e.g. RTO and GRD_CHK bits). The sdparm(8) utility can be used to
319 access and potentially change the now obsolete format mode page.
320 scsiformat is another utility available for formatting SCSI disks with
322 linux. It dates from 1997 (most recent update) and may be useful for
323 disks whose firmware is of that vintage.
324 The COUNT numeric argument may include a multiplicative suffix or be
326 given in hexadecimal. See the "NUMERIC ARGUMENTS" section in the
327 sg3_utils(8) man page.
328
330 In the first example below simply find out the existing block count and
331 size derived from two sources: a block descriptor in a MODE SELECT com‐
332 mand response and from the response of a READ CAPACITY commands. No
333 changes are made:
334 sg_format /dev/sdm
336 Now a simple format, leaving the block count and size as they were pre‐
338 viously. The FORMAT UNIT command is executed in IMMED mode and the
339 device is polled every 30 seconds to print out a progress indication:
340 sg_format --format /dev/sdm
342 Now the same format, but waiting (passively) until the format operation
344 is complete:
345 sg_format --format --wait /dev/sdm
347 Next is a format in which the block size is changed to 520 bytes and
349 the block count is set to the manufacturer's maximum value (for that
350 block size). Note, not all disks support changing the block size:
351 sg_format --format --size=520 /dev/sdm
353 Now a resize operation so that only the first 0x10000 (65536) blocks on
355 a disk are accessible. The remaining blocks remain unaltered.
356 sg_format --resize --count=0x10000 /dev/sdm
358 Now resize the disk back to its normal (maximum) block count:
360 sg_format --resize --count=-1 /dev/sdm
362 Format with type 1 protection:
364 sg_format --format --fmtpinfo=3 --pfu /dev/sdm
366
368 The exit status of sg_format is 0 when it is successful. Otherwise see
369 the sg3_utils(8) man page. Unless the --wait option is given, the exit
370 status may not reflect the success of otherwise of the format. Using
371 sg_turs(8) and sg_readcap(8) after the format operation may be wise.
372
374 Written by Grant Grundler, James Bottomley and Douglas Gilbert.
375
377 Report bugs to <dgilbert at interlog dot com>.
378
380 Copyright © 2005-2009 Grant Grundler, James Bottomley and Douglas
381 Gilbert
382 This software is distributed under the GPL version 2. There is NO war‐
383 ranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR‐
384 POSE.
385
387 sg_turs(8), sg_requests(8), sg_inq(8), sg_modes(8), sg_vpd(8), sg_reas‐
388 sign(8), sg_readcap(8) [all in sg3_utils], sdparm(8), scsiformat (old),
389 hdparm(8)
390sg3_utils-1.27 March 2009 SG_FORMAT(8)