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] [--early] [--format] [--help]
11 [--long] [--pfu=PFU] [--pinfo] [--resize] [--rto_req] [--six]
12 [--size=SIZE] [--verbose] [--version] [--wait] DEVICE
13
15 Not all SCSI direct access devices need to be formatted and some have
16 vendor specific formatting procedures. SCSI disks with rotating media
17 are probably the largest group that do support a 'standard' format
18 operation. They are typically factory formatted to a block size of 512
19 bytes with the largest number of blocks that the manufacturer recom‐
20 mends. That number of blocks typically leaves aside a certain number of
21 tracks and sectors for reassignment of logical block addresses during
22 the life of the disk.
23 This utility can format modern SCSI disks and potentially change their
25 block size (if permitted) and the block count (i.e. number of accessi‐
26 ble blocks on the media also known as "resizing"). Resizing a disk to
27 less than the manufacturer's recommended block count is sometimes
28 called "short stroking" (see NOTES section). Resizing the block count
29 while not changing the block size may not require a format operation.
30 Recent changes to the SBC-2 draft standard (see www.t10.org) have obso‐
31 leted the "format device" mode page. Many of the low level details
32 found in that mode page are now left up to the discretion of the manu‐
33 facturer.
34 When this utility is used without options (apart from a device name)
36 then it prints out the existing block size and block count derived from
37 two sources. These two sources are a block descriptor in the response
38 to a MODE SENSE command and the response to a READ CAPACITY command.
39 The reason for this double check is to detect a "format corrupt" state
40 (see NOTES section).
41 A recent addition in the SBC-2 is "protection information". See the
43 section of that name (section 4.16 in draft SBC-2 rev 16). It adds an
44 extra 8 bytes of protection information to each block (a 2 byte "logi‐
45 cal block guard" (CRC), a 2 byte "logical block application guard", and
46 a 4 byte "logical block reference tag"). A device that supports protec‐
47 tion information sets the "protect" bit in a standard INQUIRY response.
48 The "FMTPINFO" and "RTO_REQ" bits in the FORMAT command cdb are associ‐
49 ated with protection information and can be set by this utility.
50
52 Arguments to long options are mandatory for short options as well.
53 -C, --cmplst=0 | 1
55 sets the CMPLST ("complete list") bit in the FORMAT cdb to 0 or
56 1. The default is 1 in which case the existing GLIST (grown
57 list) is ignored. If the value is 0 then th existing GLIST is
58 taken into account. See the LISTS section below. Active when the
59 --format option is given. In most cases this bit should be left
60 set; some MO disk drives need this bit cleared. The SCSI to ATA
61 Translation (SAT) draft standard (sat-r09) requires this bit to
62 be cleared.
63 -c, --count=COUNT
65 where COUNT is the number of blocks to be formatted or media to
66 be resized to. Can be used with either --format or --resize.
67 With --format this option need not be given in which case it is
68 assumed to be zero. With --format the interpretation of COUNT
69 is:
70 (COUNT > 0) : only format the first COUNT blocks and READ
71 CAPACITY will report COUNT blocks after format
72 (COUNT = 0) and block size unchanged : use existing block
73 count
74 (COUNT = 0) and block size changed : recommended maximum block
75 count for new block size
76 (COUNT = -1) : use recommended maximum block count
77 (COUNT < -1) : illegal
78 With --resize this option must be given and COUNT has this
79 interpretation:
80 (COUNT > 0) : after resize READ CAPACITY will report COUNT
81 blocks
82 (COUNT = 0) : after resize READ CAPACITY will report 0 blocks
83 (COUNT = -1) : after resize READ CAPACITY will report its
84 maximum number of blocks
85 (COUNT < -1) : illegal
86 In both cases if the given COUNT exceeds the maximum number of
87 blocks (for the block size) then the disk reports an error. See
88 NOTES section below.
89 -e, --early
91 this option is active when --format is given. The default action
92 of this utility is to poll the disk every 30 seconds to deter‐
93 mine the progress of the format operation until it is finished.
94 When this option is given this utility will exit "early" as soon
95 as the format has commenced. Then the user can monitor the
96 progress of the ongoing format operation with other utilities
97 (e.g. sg_turs or sg_requests). This option and --wait cannot
98 both be given.
99 -F, --format
101 issue a SCSI FORMAT command. This will destroy all the data
102 held on the media. This option is required to change the block
103 size of a disk. The user is given a 10 second count down to
104 ponder the wisdom of doing this, during which time control-C
105 (amongst other Unix commands) can be used to kill this process
106 before it does any damage. See NOTES section for implementation
107 details and EXAMPLES section for typical use.
108 -h, --help
110 print out the usage information then exit.
111 -l, --long
113 the default action of this utility is to assume 32 bit logical
114 block addresses. With 512 byte block size this permits almost 2
115 terabytes (almost 2 ** 41 bytes) on a single disk. This option
116 selects commands and parameters that allow for 64 bit logical
117 block addresses. Specifically this is the "longlba" flag in the
118 MODE SENSE (10) command and READ CAPACITY (16) rather than READ
119 CAPACITY (10). When a disk supports "protection information"
120 then this option may also be useful.
121 -P, --pfu=PFU
123 sets the "Protection Field Usage" field in the parameter block
124 associated with a FORMAT command to PFU. The default value is 0,
125 values in the range 0 to 7 may be given.
126 -p, --pinfo
128 instructs a format operation to add an extra 8 bytes of protec‐
129 tion information by setting the FMTPINFO bit in the FORMAT com‐
130 mand cdb. Default action is not to format with protection infor‐
131 mation. Has no action unless --format is given.
132 -r, --resize
134 rather than format the disk, it can be resized. This means
135 changing the number of blocks on the device reported by the READ
136 CAPACITY command. This option should be used with the
137 --count=COUNT option. The contents of all logical blocks on the
138 media remain unchanged when this option is used. This means that
139 any resize operation can be reversed. This option cannot be used
140 together with either --format or a --size=SIZE whose argument is
141 different to the existing block size.
142 -R, --rto_req
144 instructs a format to enable application client ownership of the
145 "logical block reference tag" field (i.e. the RTO_REQ bit in the
146 FORMAT cdb). The default action is to disable application client
147 ownership of that field. Has no action unless both --format and
148 --pinfo are given.
149 -6, --six
151 Use 6 byte variants of MODE SENSE and MODE SELECT. The default
152 action is to use the 10 byte variants. Some MO drives need this
153 option set when doing a format.
154 -s, --size=SIZE
156 where SIZE is the block size (i.e. number of bytes in each
157 block) to format the device to. The default value is whatever
158 is currently reported by the block descriptor in a MODE SENSE
159 command. This option is only active when the --format option is
160 also given. If the block size given by this option is different
161 from the current value then a MODE SELECT command is used to
162 change it prior to the FORMAT command being started (as recom‐
163 mended in the draft standard). Recent SCSI disks usually have
164 512 byte sectors by default and allow up to 16 bytes extra in a
165 sector (i.e. 528 byte sectors). If the given size in unaccept‐
166 able to the disk, most likely an "Invalid field in parameter
167 list" message will appear in sense data (requires the use of
168 '-v' to decode sense data).
169 -v, --verbose
171 increase the level of verbosity, (i.e. debug output). "-vvv"
172 gives the maximum debug output.
173 -V, --version
175 print the version string and then exit.
176 -w, --wait
178 this option only has an effect when used together with the
179 --format option. The default format action is to set the "IMMED"
180 bit in the FORMAT UNIT command's (short) parameter header. If
181 this option (i.e. --wait) is given then the "IMMED" bit is not
182 set. Then the FORMAT UNIT command waits until the format opera‐
183 tion completes before returning its response. This can be sev‐
184 eral hours on large disks. This utility sets a four hour timeout
185 on such a FORMAT UNIT command.
186
188 The SBC-3 draft (revision 6) defines PLIST, CLIST, DLIST and GLIST in
189 section 4.8 on "Medium defects". Briefly, the PLIST is the "primary"
190 list of manufacturer detected defects, the CLIST ("certification" list)
191 are those detected during the format operation, the DLIST is a list of
192 defects that can be given to the format operation. The GLIST is the
193 grown list which starts in the format process as CLIST+DLIST and can
194 "grow" later due to automatic reallocation (see the ARRE and AWRE bits
195 in the read-write error recovery mode page (see sdparm)) and use of the
196 SCSI REASSIGN BLOCKS command (see sg_reassign).
197 The CMPLST bit (controlled by the --cmplst=0|1 option) determines
199 whether the existing GLIST, when the format operation is invoked, is
200 taken into account. The sg_format utility sets the FOV bit to zero
201 which causes the DPRY=0, so the PLIST is taken into account, and
202 DCRT=0, so the CLIST is generated and used during the format process.
203 The sg_format utility does not permit a user to provide a defect list
205 (i.e. DLIST). All protection information options are defaulted to off.
206
208 The SBC-2 draft standard (revision 16) says that the REQUEST SENSE com‐
209 mand should be used for obtaining a progress indication when the format
210 command returns prior to the completion of the format operation. How‐
211 ever, tests on a selection of recent disks shows that TEST UNIT READY
212 commands yield progress indications (but not REQUEST SENSE commands). A
213 new option may be required to handle this when disks catch up to the
214 current draft.
215 When the --format option is given then there is a 10 second window dur‐
217 ing which the user is invited to abort sg_format. This is just prior
218 the SCSI FORMAT UNIT command being issued. If the --wait option is not
219 given then the SCSI FORMAT UNIT command is issued with the IMMED bit
220 set which causes the SCSI command to return after it has started the
221 format operation. The --early option will cause sg_format to exit at
222 that point. Otherwise the DEVICE is polled every 30 seconds with TEST
223 UNIT READY commands until it reports an "all clear" (i.e. the format
224 operation has completed). Normally these polling commands will result
225 in a progress indicator (expressed as a percentage) being output to the
226 screen. If the user gets bored watching the progress report then
227 sg_format process can be terminated (e.g. with control-C) without
228 affecting the format operation which continues. However a bus or device
229 reset (or a power cycle) may well cause the device to become "format
230 corrupt".
231 When the --format and --wait options are both given then this utility
233 may take a long time to return. In this case care should be taken not
234 to send any other SCSI commands to the disk as it may not respon leav‐
235 ing those commands queued behind the active format command. This may
236 cause a timeout in the OS driver (in a lot shorter period than 4 hours
237 applicable to the format command). This may result in the OS resetting
238 the disk leaving the format operation incomplete. This may leave the
239 disk in a "format corrupt" state requiring another format to remedy the
240 situation.
241 When the block size (i.e. the number of bytes in each block) is changed
243 on a disk two SCSI commands must be sent: a MODE SELECT to change the
244 block size followed by a FORMAT command. If the MODE SELECT command
245 succeeds and the FORMAT fails then the disk may be in a state that the
246 draft standard calls "format corrupt". A block descriptor in a subse‐
247 quent MODE SENSE will report the requested new block size while a READ
248 CAPACITY command will report the existing (i.e. different) block size.
249 Alternatively the READ CAPACITY command may fail, reporting the device
250 is not ready, potentially requiring a format. The solution to this sit‐
251 uation is to do a format again (and this time the new block size does
252 not have to be given) or change the block size back to the original
253 size.
254 The draft SBC-2 standard states that the block count can be set back to
256 the manufacturer's maximum recommended value in a format or resize
257 operation. This can be done by placing an address of 0xffffffff (or the
258 64 bit equivalent) in the appropriate block descriptor field to a MODE
259 SELECT command. In signed (two's complement) arithmetic that value cor‐
260 responds to '-1'. So a --count=-1 causes the block count to be set back
261 to the manufacturer's maximum recommended value. To see exactly which
262 SCSI commands are being executed and parameters passed add "-vvv" to
263 the sg_format command line.
264 Short stroking is a technique to trade off capacity for performance.
266 Disk performance is usually highest on the outer tracks (i.e. lower
267 logical block addresses) so by resizing or reformatting a disk to a
268 smaller capacity, average performance will usually be increased.
269 Other utilities may be useful in finding information associated with
271 formatting. These include sg_inq to fetch standard INQUIRY information
272 (e.g. the PROTECT bit) and to fetch the extended INQUIRY VPD page (e.g.
273 RTO and GRD_CHK bits). The sdparm (or sginfo) utility can be used to
274 access and potentially change the now obsolete format mode page.
275 scsiformat is another utility available for formatting SCSI disks with
277 linux. It dates from 1997 (most recent update) and may be useful for
278 disks whose firmware is of that vintage.
279 The COUNT value is a number which may be followed by one of these mul‐
281 tiplicative suffixes: c C *1; w W *2; b B *512; k K KiB *1,024; KB
282 *1,000; m M MiB *1,048,576; MB *1,000,000 . This pattern continues for
283 "G", "T" and "P". Also a suffix of the form "x<n>" multiplies the lead‐
284 ing number by <n>. Alternatively numerical values can be given in hexa‐
285 decimal preceded by either "0x" or "0X" (or with a trailing "h" or
286 "H"). When hex numbers are given, multipliers cannot be used.
287
289 First, do not alter anything but print out the existing block count and
290 size derived from two sources: a block descriptor in a MODE SELECT com‐
291 mand response and from the response of a READ CAPACITY commands:
292 sg_format /dev/sdm
294 Now a simple format, leaving the block count and size as they were pre‐
296 viously. The FORMAT command is executed in IMMED mode and the device is
297 polled every 30 seconds to print out a progress indication:
298 sg_format --format /dev/sdm
300 Now the same format, but waiting (passively) until the format operation
302 is complete:
303 sg_format --format --wait /dev/sdm
305 Next is a format in which the block size is changed to 520 bytes and
307 the block count is set to the manufacturer's maximum value (for that
308 block size). Note, not all disks support changing the block size:
309 sg_format --format --size=520 /dev/sdm
311 Now a resize operation so that only the first 0x10000 (65536) blocks on
313 a disk are accessible. The remaining blocks remain unaltered.
314 sg_format --resize --count=0x10000 /dev/sdm
316 Now resize the disk back to its normal (maximum) block count:
318 sg_format --resize --count=-1 /dev/sdm
320
322 The exit status of sg_format is 0 when it is successful. Otherwise see
323 the sg3_utils(8) man page. Unless the --wait option is given, the exit
324 status may not reflect to success of otherwise of the format. Using
325 sg_turs and sg_readcap after the format operation may be wise.
326
328 Written by Grant Grundler, James Bottomley and Douglas Gilbert.
329
331 Report bugs to <dgilbert at interlog dot com>.
332
334 Copyright © 2005-2007 Grant Grundler, James Bottomley and Douglas
335 Gilbert
336 This software is distributed under the GPL version 2. There is NO war‐
337 ranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR‐
338 POSE.
339
341 sg_turs, sg_requests, sg_inq, sg_modes, sginfo, sg_reassign (all in
342 sg3_utils), sdparm, scsiformat, setblocksize
343sg3_utils-1.23 January 2007 SG_FORMAT(8)