1 What: /sys/block/<disk>/alignment_of 1 What: /sys/block/<disk>/alignment_offset
2 Date: April 2009 2 Date: April 2009
3 Contact: Martin K. Petersen <martin.pete 3 Contact: Martin K. Petersen <martin.petersen@oracle.com>
4 Description: 4 Description:
5 Storage devices may report a p 5 Storage devices may report a physical block size that is
6 bigger than the logical block 6 bigger than the logical block size (for instance a drive
7 with 4KB physical sectors expo 7 with 4KB physical sectors exposing 512-byte logical
8 blocks to the operating system 8 blocks to the operating system). This parameter
9 indicates how many bytes the b 9 indicates how many bytes the beginning of the device is
10 offset from the disk's natural 10 offset from the disk's natural alignment.
11 11
12 12
13 What: /sys/block/<disk>/discard_alig 13 What: /sys/block/<disk>/discard_alignment
14 Date: May 2011 14 Date: May 2011
15 Contact: Martin K. Petersen <martin.pete 15 Contact: Martin K. Petersen <martin.petersen@oracle.com>
16 Description: 16 Description:
17 Devices that support discard f 17 Devices that support discard functionality may
18 internally allocate space in u 18 internally allocate space in units that are bigger than
19 the exported logical block siz 19 the exported logical block size. The discard_alignment
20 parameter indicates how many b 20 parameter indicates how many bytes the beginning of the
21 device is offset from the inte 21 device is offset from the internal allocation unit's
22 natural alignment. 22 natural alignment.
23 23
24 What: /sys/block/<disk>/atomic_write <<
25 Date: February 2024 <<
26 Contact: Himanshu Madhani <himanshu.madh <<
27 Description: <<
28 [RO] This parameter specifies <<
29 size reported by the device. T <<
30 for merging of writes, where a <<
31 operation must not exceed this <<
32 This parameter may be greater <<
33 atomic_write_unit_max_bytes as <<
34 atomic_write_unit_max_bytes wi <<
35 power-of-two and atomic_write_ <<
36 limited by some other queue li <<
37 This parameter - along with at <<
38 and atomic_write_unit_max_byte <<
39 max_hw_sectors_kb, but may be <<
40 <<
41 <<
42 What: /sys/block/<disk>/atomic_write <<
43 Date: February 2024 <<
44 Contact: Himanshu Madhani <himanshu.madh <<
45 Description: <<
46 [RO] This parameter specifies <<
47 be written atomically with an <<
48 atomic write operations must b <<
49 atomic_write_unit_min boundary <<
50 atomic_write_unit_min. This va <<
51 <<
52 <<
53 What: /sys/block/<disk>/atomic_write <<
54 Date: February 2024 <<
55 Contact: Himanshu Madhani <himanshu.madh <<
56 Description: <<
57 [RO] This parameter defines th <<
58 written atomically with an ato <<
59 value must be a multiple of at <<
60 be a power-of-two. This value <<
61 atomic_write_max_bytes. <<
62 <<
63 <<
64 What: /sys/block/<disk>/atomic_write <<
65 Date: February 2024 <<
66 Contact: Himanshu Madhani <himanshu.madh <<
67 Description: <<
68 [RO] A device may need to inte <<
69 which straddles a given logica <<
70 parameter specifies the size i <<
71 one is reported by the device. <<
72 power-of-two and at least the <<
73 atomic_write_unit_max_bytes. <<
74 Any attempt to merge atomic wr <<
75 merged I/O which crosses this <<
76 <<
77 24
78 What: /sys/block/<disk>/diskseq 25 What: /sys/block/<disk>/diskseq
79 Date: February 2021 26 Date: February 2021
80 Contact: Matteo Croce <mcroce@microsoft. 27 Contact: Matteo Croce <mcroce@microsoft.com>
81 Description: 28 Description:
82 The /sys/block/<disk>/diskseq 29 The /sys/block/<disk>/diskseq files reports the disk
83 sequence number, which is a mo 30 sequence number, which is a monotonically increasing
84 number assigned to every drive 31 number assigned to every drive.
85 Some devices, like the loop de 32 Some devices, like the loop device, refresh such number
86 every time the backing file is 33 every time the backing file is changed.
87 The value type is 64 bit unsig 34 The value type is 64 bit unsigned.
88 35
89 36
90 What: /sys/block/<disk>/inflight 37 What: /sys/block/<disk>/inflight
91 Date: October 2009 38 Date: October 2009
92 Contact: Jens Axboe <axboe@kernel.dk>, N 39 Contact: Jens Axboe <axboe@kernel.dk>, Nikanth Karthikesan <knikanth@suse.de>
93 Description: 40 Description:
94 Reports the number of I/O requ 41 Reports the number of I/O requests currently in progress
95 (pending / in flight) in a dev 42 (pending / in flight) in a device driver. This can be less
96 than the number of requests qu 43 than the number of requests queued in the block device queue.
97 The report contains 2 fields: 44 The report contains 2 fields: one for read requests
98 and one for write requests. 45 and one for write requests.
99 The value type is unsigned int 46 The value type is unsigned int.
100 Cf. Documentation/block/stat.r 47 Cf. Documentation/block/stat.rst which contains a single value for
101 requests in flight. 48 requests in flight.
102 This is related to /sys/block/ 49 This is related to /sys/block/<disk>/queue/nr_requests
103 and for SCSI device also its q 50 and for SCSI device also its queue_depth.
104 51
105 52
106 What: /sys/block/<disk>/integrity/de 53 What: /sys/block/<disk>/integrity/device_is_integrity_capable
107 Date: July 2014 54 Date: July 2014
108 Contact: Martin K. Petersen <martin.pete 55 Contact: Martin K. Petersen <martin.petersen@oracle.com>
109 Description: 56 Description:
110 Indicates whether a storage de 57 Indicates whether a storage device is capable of storing
111 integrity metadata. Set if the 58 integrity metadata. Set if the device is T10 PI-capable.
112 59
113 60
114 What: /sys/block/<disk>/integrity/fo 61 What: /sys/block/<disk>/integrity/format
115 Date: June 2008 62 Date: June 2008
116 Contact: Martin K. Petersen <martin.pete 63 Contact: Martin K. Petersen <martin.petersen@oracle.com>
117 Description: 64 Description:
118 Metadata format for integrity 65 Metadata format for integrity capable block device.
119 E.g. T10-DIF-TYPE1-CRC. 66 E.g. T10-DIF-TYPE1-CRC.
120 67
121 68
122 What: /sys/block/<disk>/integrity/pr 69 What: /sys/block/<disk>/integrity/protection_interval_bytes
123 Date: July 2015 70 Date: July 2015
124 Contact: Martin K. Petersen <martin.pete 71 Contact: Martin K. Petersen <martin.petersen@oracle.com>
125 Description: 72 Description:
126 Describes the number of data b 73 Describes the number of data bytes which are protected
127 by one integrity tuple. Typica 74 by one integrity tuple. Typically the device's logical
128 block size. 75 block size.
129 76
130 77
131 What: /sys/block/<disk>/integrity/re 78 What: /sys/block/<disk>/integrity/read_verify
132 Date: June 2008 79 Date: June 2008
133 Contact: Martin K. Petersen <martin.pete 80 Contact: Martin K. Petersen <martin.petersen@oracle.com>
134 Description: 81 Description:
135 Indicates whether the block la 82 Indicates whether the block layer should verify the
136 integrity of read requests ser 83 integrity of read requests serviced by devices that
137 support sending integrity meta 84 support sending integrity metadata.
138 85
139 86
140 What: /sys/block/<disk>/integrity/ta 87 What: /sys/block/<disk>/integrity/tag_size
141 Date: June 2008 88 Date: June 2008
142 Contact: Martin K. Petersen <martin.pete 89 Contact: Martin K. Petersen <martin.petersen@oracle.com>
143 Description: 90 Description:
144 Number of bytes of integrity t 91 Number of bytes of integrity tag space available per
145 512 bytes of data. 92 512 bytes of data.
146 93
147 94
148 What: /sys/block/<disk>/integrity/wr 95 What: /sys/block/<disk>/integrity/write_generate
149 Date: June 2008 96 Date: June 2008
150 Contact: Martin K. Petersen <martin.pete 97 Contact: Martin K. Petersen <martin.petersen@oracle.com>
151 Description: 98 Description:
152 Indicates whether the block la 99 Indicates whether the block layer should automatically
153 generate checksums for write r 100 generate checksums for write requests bound for
154 devices that support receiving 101 devices that support receiving integrity metadata.
155 102
156 103
157 What: /sys/block/<disk>/partscan <<
158 Date: May 2024 <<
159 Contact: Christoph Hellwig <hch@lst.de> <<
160 Description: <<
161 The /sys/block/<disk>/partscan <<
162 scanning is enabled for the di <<
163 scanning is enabled, or "0" if <<
164 unsigned integer, but only "0" <<
165 <<
166 <<
167 What: /sys/block/<disk>/<partition>/ 104 What: /sys/block/<disk>/<partition>/alignment_offset
168 Date: April 2009 105 Date: April 2009
169 Contact: Martin K. Petersen <martin.pete 106 Contact: Martin K. Petersen <martin.petersen@oracle.com>
170 Description: 107 Description:
171 Storage devices may report a p 108 Storage devices may report a physical block size that is
172 bigger than the logical block 109 bigger than the logical block size (for instance a drive
173 with 4KB physical sectors expo 110 with 4KB physical sectors exposing 512-byte logical
174 blocks to the operating system 111 blocks to the operating system). This parameter
175 indicates how many bytes the b 112 indicates how many bytes the beginning of the partition
176 is offset from the disk's natu 113 is offset from the disk's natural alignment.
177 114
178 115
179 What: /sys/block/<disk>/<partition>/ 116 What: /sys/block/<disk>/<partition>/discard_alignment
180 Date: May 2011 117 Date: May 2011
181 Contact: Martin K. Petersen <martin.pete 118 Contact: Martin K. Petersen <martin.petersen@oracle.com>
182 Description: 119 Description:
183 Devices that support discard f 120 Devices that support discard functionality may
184 internally allocate space in u 121 internally allocate space in units that are bigger than
185 the exported logical block siz 122 the exported logical block size. The discard_alignment
186 parameter indicates how many b 123 parameter indicates how many bytes the beginning of the
187 partition is offset from the i 124 partition is offset from the internal allocation unit's
188 natural alignment. 125 natural alignment.
189 126
190 127
191 What: /sys/block/<disk>/<partition>/ 128 What: /sys/block/<disk>/<partition>/stat
192 Date: February 2008 129 Date: February 2008
193 Contact: Jerome Marchand <jmarchan@redha 130 Contact: Jerome Marchand <jmarchan@redhat.com>
194 Description: 131 Description:
195 The /sys/block/<disk>/<partiti 132 The /sys/block/<disk>/<partition>/stat files display the
196 I/O statistics of partition <p 133 I/O statistics of partition <partition>. The format is the
197 same as the format of /sys/blo 134 same as the format of /sys/block/<disk>/stat.
198 135
199 136
200 What: /sys/block/<disk>/queue/add_ra 137 What: /sys/block/<disk>/queue/add_random
201 Date: June 2010 138 Date: June 2010
202 Contact: linux-block@vger.kernel.org 139 Contact: linux-block@vger.kernel.org
203 Description: 140 Description:
204 [RW] This file allows to turn 141 [RW] This file allows to turn off the disk entropy contribution.
205 Default value of this file is 142 Default value of this file is '1'(on).
206 143
207 144
208 What: /sys/block/<disk>/queue/chunk_ 145 What: /sys/block/<disk>/queue/chunk_sectors
209 Date: September 2016 146 Date: September 2016
210 Contact: Hannes Reinecke <hare@suse.com> 147 Contact: Hannes Reinecke <hare@suse.com>
211 Description: 148 Description:
212 [RO] chunk_sectors has differe 149 [RO] chunk_sectors has different meaning depending on the type
213 of the disk. For a RAID device 150 of the disk. For a RAID device (dm-raid), chunk_sectors
214 indicates the size in 512B sec 151 indicates the size in 512B sectors of the RAID volume stripe
215 segment. For a zoned block dev 152 segment. For a zoned block device, either host-aware or
216 host-managed, chunk_sectors in 153 host-managed, chunk_sectors indicates the size in 512B sectors
217 of the zones of the device, wi 154 of the zones of the device, with the eventual exception of the
218 last zone of the device which 155 last zone of the device which may be smaller.
219 156
220 157
221 What: /sys/block/<disk>/queue/crypto 158 What: /sys/block/<disk>/queue/crypto/
222 Date: February 2022 159 Date: February 2022
223 Contact: linux-block@vger.kernel.org 160 Contact: linux-block@vger.kernel.org
224 Description: 161 Description:
225 The presence of this subdirect 162 The presence of this subdirectory of /sys/block/<disk>/queue/
226 indicates that the device supp 163 indicates that the device supports inline encryption. This
227 subdirectory contains files wh 164 subdirectory contains files which describe the inline encryption
228 capabilities of the device. F 165 capabilities of the device. For more information about inline
229 encryption, refer to Documenta 166 encryption, refer to Documentation/block/inline-encryption.rst.
230 167
231 168
232 What: /sys/block/<disk>/queue/crypto 169 What: /sys/block/<disk>/queue/crypto/max_dun_bits
233 Date: February 2022 170 Date: February 2022
234 Contact: linux-block@vger.kernel.org 171 Contact: linux-block@vger.kernel.org
235 Description: 172 Description:
236 [RO] This file shows the maxim 173 [RO] This file shows the maximum length, in bits, of data unit
237 numbers accepted by the device 174 numbers accepted by the device in inline encryption requests.
238 175
239 176
240 What: /sys/block/<disk>/queue/crypto 177 What: /sys/block/<disk>/queue/crypto/modes/<mode>
241 Date: February 2022 178 Date: February 2022
242 Contact: linux-block@vger.kernel.org 179 Contact: linux-block@vger.kernel.org
243 Description: 180 Description:
244 [RO] For each crypto mode (i.e 181 [RO] For each crypto mode (i.e., encryption/decryption
245 algorithm) the device supports 182 algorithm) the device supports with inline encryption, a file
246 will exist at this location. 183 will exist at this location. It will contain a hexadecimal
247 number that is a bitmask of th 184 number that is a bitmask of the supported data unit sizes, in
248 bytes, for that crypto mode. 185 bytes, for that crypto mode.
249 186
250 Currently, the crypto modes th 187 Currently, the crypto modes that may be supported are:
251 188
252 * AES-256-XTS 189 * AES-256-XTS
253 * AES-128-CBC-ESSIV 190 * AES-128-CBC-ESSIV
254 * Adiantum 191 * Adiantum
255 192
256 For example, if a device suppo 193 For example, if a device supports AES-256-XTS inline encryption
257 with data unit sizes of 512 an 194 with data unit sizes of 512 and 4096 bytes, the file
258 /sys/block/<disk>/queue/crypto 195 /sys/block/<disk>/queue/crypto/modes/AES-256-XTS will exist and
259 will contain "0x1200". 196 will contain "0x1200".
260 197
261 198
262 What: /sys/block/<disk>/queue/crypto 199 What: /sys/block/<disk>/queue/crypto/num_keyslots
263 Date: February 2022 200 Date: February 2022
264 Contact: linux-block@vger.kernel.org 201 Contact: linux-block@vger.kernel.org
265 Description: 202 Description:
266 [RO] This file shows the numbe 203 [RO] This file shows the number of keyslots the device has for
267 use with inline encryption. 204 use with inline encryption.
268 205
269 206
270 What: /sys/block/<disk>/queue/dax 207 What: /sys/block/<disk>/queue/dax
271 Date: June 2016 208 Date: June 2016
272 Contact: linux-block@vger.kernel.org 209 Contact: linux-block@vger.kernel.org
273 Description: 210 Description:
274 [RO] This file indicates wheth 211 [RO] This file indicates whether the device supports Direct
275 Access (DAX), used by CPU-addr 212 Access (DAX), used by CPU-addressable storage to bypass the
276 pagecache. It shows '1' if tr 213 pagecache. It shows '1' if true, '0' if not.
277 214
278 215
279 What: /sys/block/<disk>/queue/discar 216 What: /sys/block/<disk>/queue/discard_granularity
280 Date: May 2011 217 Date: May 2011
281 Contact: Martin K. Petersen <martin.pete 218 Contact: Martin K. Petersen <martin.petersen@oracle.com>
282 Description: 219 Description:
283 [RO] Devices that support disc 220 [RO] Devices that support discard functionality may internally
284 allocate space using units tha 221 allocate space using units that are bigger than the logical
285 block size. The discard_granul 222 block size. The discard_granularity parameter indicates the size
286 of the internal allocation uni 223 of the internal allocation unit in bytes if reported by the
287 device. Otherwise the discard_ 224 device. Otherwise the discard_granularity will be set to match
288 the device's physical block si 225 the device's physical block size. A discard_granularity of 0
289 means that the device does not 226 means that the device does not support discard functionality.
290 227
291 228
292 What: /sys/block/<disk>/queue/discar 229 What: /sys/block/<disk>/queue/discard_max_bytes
293 Date: May 2011 230 Date: May 2011
294 Contact: Martin K. Petersen <martin.pete 231 Contact: Martin K. Petersen <martin.petersen@oracle.com>
295 Description: 232 Description:
296 [RW] While discard_max_hw_byte 233 [RW] While discard_max_hw_bytes is the hardware limit for the
297 device, this setting is the so 234 device, this setting is the software limit. Some devices exhibit
298 large latencies when large dis 235 large latencies when large discards are issued, setting this
299 value lower will make Linux is 236 value lower will make Linux issue smaller discards and
300 potentially help reduce latenc 237 potentially help reduce latencies induced by large discard
301 operations. 238 operations.
302 239
303 240
304 What: /sys/block/<disk>/queue/discar 241 What: /sys/block/<disk>/queue/discard_max_hw_bytes
305 Date: July 2015 242 Date: July 2015
306 Contact: linux-block@vger.kernel.org 243 Contact: linux-block@vger.kernel.org
307 Description: 244 Description:
308 [RO] Devices that support disc 245 [RO] Devices that support discard functionality may have
309 internal limits on the number 246 internal limits on the number of bytes that can be trimmed or
310 unmapped in a single operation 247 unmapped in a single operation. The `discard_max_hw_bytes`
311 parameter is set by the device 248 parameter is set by the device driver to the maximum number of
312 bytes that can be discarded in 249 bytes that can be discarded in a single operation. Discard
313 requests issued to the device 250 requests issued to the device must not exceed this limit. A
314 `discard_max_hw_bytes` value o 251 `discard_max_hw_bytes` value of 0 means that the device does not
315 support discard functionality. 252 support discard functionality.
316 253
317 254
318 What: /sys/block/<disk>/queue/discar 255 What: /sys/block/<disk>/queue/discard_zeroes_data
319 Date: May 2011 256 Date: May 2011
320 Contact: Martin K. Petersen <martin.pete 257 Contact: Martin K. Petersen <martin.petersen@oracle.com>
321 Description: 258 Description:
322 [RO] Will always return 0. Do 259 [RO] Will always return 0. Don't rely on any specific behavior
323 for discards, and don't read t 260 for discards, and don't read this file.
324 261
325 262
326 What: /sys/block/<disk>/queue/dma_al 263 What: /sys/block/<disk>/queue/dma_alignment
327 Date: May 2022 264 Date: May 2022
328 Contact: linux-block@vger.kernel.org 265 Contact: linux-block@vger.kernel.org
329 Description: 266 Description:
330 Reports the alignment that use 267 Reports the alignment that user space addresses must have to be
331 used for raw block device acce 268 used for raw block device access with O_DIRECT and other driver
332 specific passthrough mechanism 269 specific passthrough mechanisms.
333 270
334 271
335 What: /sys/block/<disk>/queue/fua 272 What: /sys/block/<disk>/queue/fua
336 Date: May 2018 273 Date: May 2018
337 Contact: linux-block@vger.kernel.org 274 Contact: linux-block@vger.kernel.org
338 Description: 275 Description:
339 [RO] Whether or not the block 276 [RO] Whether or not the block driver supports the FUA flag for
340 write requests. FUA stands fo 277 write requests. FUA stands for Force Unit Access. If the FUA
341 flag is set that means that wr 278 flag is set that means that write requests must bypass the
342 volatile cache of the storage 279 volatile cache of the storage device.
343 280
344 281
345 What: /sys/block/<disk>/queue/hw_sec 282 What: /sys/block/<disk>/queue/hw_sector_size
346 Date: January 2008 283 Date: January 2008
347 Contact: linux-block@vger.kernel.org 284 Contact: linux-block@vger.kernel.org
348 Description: 285 Description:
349 [RO] This is the hardware sect 286 [RO] This is the hardware sector size of the device, in bytes.
350 287
351 288
352 What: /sys/block/<disk>/queue/indepe 289 What: /sys/block/<disk>/queue/independent_access_ranges/
353 Date: October 2021 290 Date: October 2021
354 Contact: linux-block@vger.kernel.org 291 Contact: linux-block@vger.kernel.org
355 Description: 292 Description:
356 [RO] The presence of this sub- 293 [RO] The presence of this sub-directory of the
357 /sys/block/xxx/queue/ director 294 /sys/block/xxx/queue/ directory indicates that the device is
358 capable of executing requests 295 capable of executing requests targeting different sector ranges
359 in parallel. For instance, sin 296 in parallel. For instance, single LUN multi-actuator hard-disks
360 will have an independent_acces 297 will have an independent_access_ranges directory if the device
361 correctly advertises the secto 298 correctly advertises the sector ranges of its actuators.
362 299
363 The independent_access_ranges 300 The independent_access_ranges directory contains one directory
364 per access range, with each ra 301 per access range, with each range described using the sector
365 (RO) attribute file to indicat 302 (RO) attribute file to indicate the first sector of the range
366 and the nr_sectors (RO) attrib 303 and the nr_sectors (RO) attribute file to indicate the total
367 number of sectors in the range 304 number of sectors in the range starting from the first sector of
368 the range. For example, a dua 305 the range. For example, a dual-actuator hard-disk will have the
369 following independent_access_r 306 following independent_access_ranges entries.::
370 307
371 $ tree /sys/block/<dis 308 $ tree /sys/block/<disk>/queue/independent_access_ranges/
372 /sys/block/<disk>/queu 309 /sys/block/<disk>/queue/independent_access_ranges/
373 |-- 0 310 |-- 0
374 | |-- nr_sectors 311 | |-- nr_sectors
375 | `-- sector 312 | `-- sector
376 `-- 1 313 `-- 1
377 |-- nr_sectors 314 |-- nr_sectors
378 `-- sector 315 `-- sector
379 316
380 The sector and nr_sectors attr 317 The sector and nr_sectors attributes use 512B sector unit,
381 regardless of the actual block 318 regardless of the actual block size of the device. Independent
382 access ranges do not overlap a 319 access ranges do not overlap and include all sectors within the
383 device capacity. The access ra 320 device capacity. The access ranges are numbered in increasing
384 order of the range start secto 321 order of the range start sector, that is, the sector attribute
385 of range 0 always has the valu 322 of range 0 always has the value 0.
386 323
387 324
388 What: /sys/block/<disk>/queue/io_pol 325 What: /sys/block/<disk>/queue/io_poll
389 Date: November 2015 326 Date: November 2015
390 Contact: linux-block@vger.kernel.org 327 Contact: linux-block@vger.kernel.org
391 Description: 328 Description:
392 [RW] When read, this file show 329 [RW] When read, this file shows whether polling is enabled (1)
393 or disabled (0). Writing '0' 330 or disabled (0). Writing '0' to this file will disable polling
394 for this device. Writing any 331 for this device. Writing any non-zero value will enable this
395 feature. 332 feature.
396 333
397 334
398 What: /sys/block/<disk>/queue/io_pol 335 What: /sys/block/<disk>/queue/io_poll_delay
399 Date: November 2016 336 Date: November 2016
400 Contact: linux-block@vger.kernel.org 337 Contact: linux-block@vger.kernel.org
401 Description: 338 Description:
402 [RW] This was used to control 339 [RW] This was used to control what kind of polling will be
403 performed. It is now fixed to 340 performed. It is now fixed to -1, which is classic polling.
404 In this mode, the CPU will rep 341 In this mode, the CPU will repeatedly ask for completions
405 without giving up any time. 342 without giving up any time.
406 <deprecated> 343 <deprecated>
407 344
408 345
409 What: /sys/block/<disk>/queue/io_tim 346 What: /sys/block/<disk>/queue/io_timeout
410 Date: November 2018 347 Date: November 2018
411 Contact: Weiping Zhang <zhangweiping@did 348 Contact: Weiping Zhang <zhangweiping@didiglobal.com>
412 Description: 349 Description:
413 [RW] io_timeout is the request 350 [RW] io_timeout is the request timeout in milliseconds. If a
414 request does not complete in t 351 request does not complete in this time then the block driver
415 timeout handler is invoked. Th 352 timeout handler is invoked. That timeout handler can decide to
416 retry the request, to fail it 353 retry the request, to fail it or to start a device recovery
417 strategy. 354 strategy.
418 355
419 356
420 What: /sys/block/<disk>/queue/iostat 357 What: /sys/block/<disk>/queue/iostats
421 Date: January 2009 358 Date: January 2009
422 Contact: linux-block@vger.kernel.org 359 Contact: linux-block@vger.kernel.org
423 Description: 360 Description:
424 [RW] This file is used to cont 361 [RW] This file is used to control (on/off) the iostats
425 accounting of the disk. 362 accounting of the disk.
426 363
427 364
428 What: /sys/block/<disk>/queue/logica 365 What: /sys/block/<disk>/queue/logical_block_size
429 Date: May 2009 366 Date: May 2009
430 Contact: Martin K. Petersen <martin.pete 367 Contact: Martin K. Petersen <martin.petersen@oracle.com>
431 Description: 368 Description:
432 [RO] This is the smallest unit 369 [RO] This is the smallest unit the storage device can address.
433 It is typically 512 bytes. 370 It is typically 512 bytes.
434 371
435 372
436 What: /sys/block/<disk>/queue/max_ac 373 What: /sys/block/<disk>/queue/max_active_zones
437 Date: July 2020 374 Date: July 2020
438 Contact: Niklas Cassel <niklas.cassel@wd 375 Contact: Niklas Cassel <niklas.cassel@wdc.com>
439 Description: 376 Description:
440 [RO] For zoned block devices ( 377 [RO] For zoned block devices (zoned attribute indicating
441 "host-managed" or "host-aware" 378 "host-managed" or "host-aware"), the sum of zones belonging to
442 any of the zone states: EXPLIC 379 any of the zone states: EXPLICIT OPEN, IMPLICIT OPEN or CLOSED,
443 is limited by this value. If t 380 is limited by this value. If this value is 0, there is no limit.
444 381
445 If the host attempts to exceed 382 If the host attempts to exceed this limit, the driver should
446 report this error with BLK_STS 383 report this error with BLK_STS_ZONE_ACTIVE_RESOURCE, which user
447 space may see as the EOVERFLOW 384 space may see as the EOVERFLOW errno.
448 385
449 386
450 What: /sys/block/<disk>/queue/max_di 387 What: /sys/block/<disk>/queue/max_discard_segments
451 Date: February 2017 388 Date: February 2017
452 Contact: linux-block@vger.kernel.org 389 Contact: linux-block@vger.kernel.org
453 Description: 390 Description:
454 [RO] The maximum number of DMA 391 [RO] The maximum number of DMA scatter/gather entries in a
455 discard request. 392 discard request.
456 393
457 394
458 What: /sys/block/<disk>/queue/max_hw 395 What: /sys/block/<disk>/queue/max_hw_sectors_kb
459 Date: September 2004 396 Date: September 2004
460 Contact: linux-block@vger.kernel.org 397 Contact: linux-block@vger.kernel.org
461 Description: 398 Description:
462 [RO] This is the maximum numbe 399 [RO] This is the maximum number of kilobytes supported in a
463 single data transfer. 400 single data transfer.
464 401
465 402
466 What: /sys/block/<disk>/queue/max_in 403 What: /sys/block/<disk>/queue/max_integrity_segments
467 Date: September 2010 404 Date: September 2010
468 Contact: linux-block@vger.kernel.org 405 Contact: linux-block@vger.kernel.org
469 Description: 406 Description:
470 [RO] Maximum number of element 407 [RO] Maximum number of elements in a DMA scatter/gather list
471 with integrity data that will 408 with integrity data that will be submitted by the block layer
472 core to the associated block d 409 core to the associated block driver.
473 410
474 411
475 What: /sys/block/<disk>/queue/max_op 412 What: /sys/block/<disk>/queue/max_open_zones
476 Date: July 2020 413 Date: July 2020
477 Contact: Niklas Cassel <niklas.cassel@wd 414 Contact: Niklas Cassel <niklas.cassel@wdc.com>
478 Description: 415 Description:
479 [RO] For zoned block devices ( 416 [RO] For zoned block devices (zoned attribute indicating
480 "host-managed" or "host-aware" 417 "host-managed" or "host-aware"), the sum of zones belonging to
481 any of the zone states: EXPLIC 418 any of the zone states: EXPLICIT OPEN or IMPLICIT OPEN, is
482 limited by this value. If this 419 limited by this value. If this value is 0, there is no limit.
483 420
484 421
485 What: /sys/block/<disk>/queue/max_se 422 What: /sys/block/<disk>/queue/max_sectors_kb
486 Date: September 2004 423 Date: September 2004
487 Contact: linux-block@vger.kernel.org 424 Contact: linux-block@vger.kernel.org
488 Description: 425 Description:
489 [RW] This is the maximum numbe 426 [RW] This is the maximum number of kilobytes that the block
490 layer will allow for a filesys 427 layer will allow for a filesystem request. Must be smaller than
491 or equal to the maximum size a 428 or equal to the maximum size allowed by the hardware. Write 0
492 to use default kernel settings 429 to use default kernel settings.
493 430
494 431
495 What: /sys/block/<disk>/queue/max_se 432 What: /sys/block/<disk>/queue/max_segment_size
496 Date: March 2010 433 Date: March 2010
497 Contact: linux-block@vger.kernel.org 434 Contact: linux-block@vger.kernel.org
498 Description: 435 Description:
499 [RO] Maximum size in bytes of 436 [RO] Maximum size in bytes of a single element in a DMA
500 scatter/gather list. 437 scatter/gather list.
501 438
502 439
503 What: /sys/block/<disk>/queue/max_se 440 What: /sys/block/<disk>/queue/max_segments
504 Date: March 2010 441 Date: March 2010
505 Contact: linux-block@vger.kernel.org 442 Contact: linux-block@vger.kernel.org
506 Description: 443 Description:
507 [RO] Maximum number of element 444 [RO] Maximum number of elements in a DMA scatter/gather list
508 that is submitted to the assoc 445 that is submitted to the associated block driver.
509 446
510 447
511 What: /sys/block/<disk>/queue/minimu 448 What: /sys/block/<disk>/queue/minimum_io_size
512 Date: April 2009 449 Date: April 2009
513 Contact: Martin K. Petersen <martin.pete 450 Contact: Martin K. Petersen <martin.petersen@oracle.com>
514 Description: 451 Description:
515 [RO] Storage devices may repor 452 [RO] Storage devices may report a granularity or preferred
516 minimum I/O size which is the 453 minimum I/O size which is the smallest request the device can
517 perform without incurring a pe 454 perform without incurring a performance penalty. For disk
518 drives this is often the physi 455 drives this is often the physical block size. For RAID arrays
519 it is often the stripe chunk s 456 it is often the stripe chunk size. A properly aligned multiple
520 of minimum_io_size is the pref 457 of minimum_io_size is the preferred request size for workloads
521 where a high number of I/O ope 458 where a high number of I/O operations is desired.
522 459
523 460
524 What: /sys/block/<disk>/queue/nomerg 461 What: /sys/block/<disk>/queue/nomerges
525 Date: January 2010 462 Date: January 2010
526 Contact: linux-block@vger.kernel.org 463 Contact: linux-block@vger.kernel.org
527 Description: 464 Description:
528 [RW] Standard I/O elevator ope 465 [RW] Standard I/O elevator operations include attempts to merge
529 contiguous I/Os. For known ran 466 contiguous I/Os. For known random I/O loads these attempts will
530 always fail and result in extr 467 always fail and result in extra cycles being spent in the
531 kernel. This allows one to tur 468 kernel. This allows one to turn off this behavior on one of two
532 ways: When set to 1, complex m 469 ways: When set to 1, complex merge checks are disabled, but the
533 simple one-shot merges with th 470 simple one-shot merges with the previous I/O request are
534 enabled. When set to 2, all me 471 enabled. When set to 2, all merge tries are disabled. The
535 default value is 0 - which ena 472 default value is 0 - which enables all types of merge tries.
536 473
537 474
538 What: /sys/block/<disk>/queue/nr_req 475 What: /sys/block/<disk>/queue/nr_requests
539 Date: July 2003 476 Date: July 2003
540 Contact: linux-block@vger.kernel.org 477 Contact: linux-block@vger.kernel.org
541 Description: 478 Description:
542 [RW] This controls how many re 479 [RW] This controls how many requests may be allocated in the
543 block layer for read or write 480 block layer for read or write requests. Note that the total
544 allocated number may be twice 481 allocated number may be twice this amount, since it applies only
545 to reads or writes (not the ac 482 to reads or writes (not the accumulated sum).
546 483
547 To avoid priority inversion th 484 To avoid priority inversion through request starvation, a
548 request queue maintains a sepa 485 request queue maintains a separate request pool per each cgroup
549 when CONFIG_BLK_CGROUP is enab 486 when CONFIG_BLK_CGROUP is enabled, and this parameter applies to
550 each such per-block-cgroup req 487 each such per-block-cgroup request pool. IOW, if there are N
551 block cgroups, each request qu 488 block cgroups, each request queue may have up to N request
552 pools, each independently regu 489 pools, each independently regulated by nr_requests.
553 490
554 491
555 What: /sys/block/<disk>/queue/nr_zon 492 What: /sys/block/<disk>/queue/nr_zones
556 Date: November 2018 493 Date: November 2018
557 Contact: Damien Le Moal <damien.lemoal@w 494 Contact: Damien Le Moal <damien.lemoal@wdc.com>
558 Description: 495 Description:
559 [RO] nr_zones indicates the to 496 [RO] nr_zones indicates the total number of zones of a zoned
560 block device ("host-aware" or 497 block device ("host-aware" or "host-managed" zone model). For
561 regular block devices, the val 498 regular block devices, the value is always 0.
562 499
563 500
564 What: /sys/block/<disk>/queue/optima 501 What: /sys/block/<disk>/queue/optimal_io_size
565 Date: April 2009 502 Date: April 2009
566 Contact: Martin K. Petersen <martin.pete 503 Contact: Martin K. Petersen <martin.petersen@oracle.com>
567 Description: 504 Description:
568 [RO] Storage devices may repor 505 [RO] Storage devices may report an optimal I/O size, which is
569 the device's preferred unit fo 506 the device's preferred unit for sustained I/O. This is rarely
570 reported for disk drives. For 507 reported for disk drives. For RAID arrays it is usually the
571 stripe width or the internal t 508 stripe width or the internal track size. A properly aligned
572 multiple of optimal_io_size is 509 multiple of optimal_io_size is the preferred request size for
573 workloads where sustained thro 510 workloads where sustained throughput is desired. If no optimal
574 I/O size is reported this file 511 I/O size is reported this file contains 0.
575 512
576 513
577 What: /sys/block/<disk>/queue/physic 514 What: /sys/block/<disk>/queue/physical_block_size
578 Date: May 2009 515 Date: May 2009
579 Contact: Martin K. Petersen <martin.pete 516 Contact: Martin K. Petersen <martin.petersen@oracle.com>
580 Description: 517 Description:
581 [RO] This is the smallest unit 518 [RO] This is the smallest unit a physical storage device can
582 write atomically. It is usual 519 write atomically. It is usually the same as the logical block
583 size but may be bigger. One e 520 size but may be bigger. One example is SATA drives with 4KB
584 sectors that expose a 512-byte 521 sectors that expose a 512-byte logical block size to the
585 operating system. For stacked 522 operating system. For stacked block devices the
586 physical_block_size variable c 523 physical_block_size variable contains the maximum
587 physical_block_size of the com 524 physical_block_size of the component devices.
588 525
589 526
590 What: /sys/block/<disk>/queue/read_a 527 What: /sys/block/<disk>/queue/read_ahead_kb
591 Date: May 2004 528 Date: May 2004
592 Contact: linux-block@vger.kernel.org 529 Contact: linux-block@vger.kernel.org
593 Description: 530 Description:
594 [RW] Maximum number of kilobyt 531 [RW] Maximum number of kilobytes to read-ahead for filesystems
595 on this block device. 532 on this block device.
596 533
597 534
598 What: /sys/block/<disk>/queue/rotati 535 What: /sys/block/<disk>/queue/rotational
599 Date: January 2009 536 Date: January 2009
600 Contact: linux-block@vger.kernel.org 537 Contact: linux-block@vger.kernel.org
601 Description: 538 Description:
602 [RW] This file is used to stat 539 [RW] This file is used to stat if the device is of rotational
603 type or non-rotational type. 540 type or non-rotational type.
604 541
605 542
606 What: /sys/block/<disk>/queue/rq_aff 543 What: /sys/block/<disk>/queue/rq_affinity
607 Date: September 2008 544 Date: September 2008
608 Contact: linux-block@vger.kernel.org 545 Contact: linux-block@vger.kernel.org
609 Description: 546 Description:
610 [RW] If this option is '1', th 547 [RW] If this option is '1', the block layer will migrate request
611 completions to the cpu "group" 548 completions to the cpu "group" that originally submitted the
612 request. For some workloads th 549 request. For some workloads this provides a significant
613 reduction in CPU cycles due to 550 reduction in CPU cycles due to caching effects.
614 551
615 For storage configurations tha 552 For storage configurations that need to maximize distribution of
616 completion processing setting 553 completion processing setting this option to '2' forces the
617 completion to run on the reque 554 completion to run on the requesting cpu (bypassing the "group"
618 aggregation logic). 555 aggregation logic).
619 556
620 557
621 What: /sys/block/<disk>/queue/schedu 558 What: /sys/block/<disk>/queue/scheduler
622 Date: October 2004 559 Date: October 2004
623 Contact: linux-block@vger.kernel.org 560 Contact: linux-block@vger.kernel.org
624 Description: 561 Description:
625 [RW] When read, this file will 562 [RW] When read, this file will display the current and available
626 IO schedulers for this block d 563 IO schedulers for this block device. The currently active IO
627 scheduler will be enclosed in 564 scheduler will be enclosed in [] brackets. Writing an IO
628 scheduler name to this file wi 565 scheduler name to this file will switch control of this block
629 device to that new IO schedule 566 device to that new IO scheduler. Note that writing an IO
630 scheduler name to this file wi 567 scheduler name to this file will attempt to load that IO
631 scheduler module, if it isn't 568 scheduler module, if it isn't already present in the system.
632 569
633 570
634 What: /sys/block/<disk>/queue/stable 571 What: /sys/block/<disk>/queue/stable_writes
635 Date: September 2020 572 Date: September 2020
636 Contact: linux-block@vger.kernel.org 573 Contact: linux-block@vger.kernel.org
637 Description: 574 Description:
638 [RW] This file will contain '1 575 [RW] This file will contain '1' if memory must not be modified
639 while it is being used in a wr 576 while it is being used in a write request to this device. When
640 this is the case and the kerne 577 this is the case and the kernel is performing writeback of a
641 page, the kernel will wait for 578 page, the kernel will wait for writeback to complete before
642 allowing the page to be modifi 579 allowing the page to be modified again, rather than allowing
643 immediate modification as is n 580 immediate modification as is normally the case. This
644 restriction arises when the de 581 restriction arises when the device accesses the memory multiple
645 times where the same data must 582 times where the same data must be seen every time -- for
646 example, once to calculate a c 583 example, once to calculate a checksum and once to actually write
647 the data. If no such restrict 584 the data. If no such restriction exists, this file will contain
648 '0'. This file is writable fo 585 '0'. This file is writable for testing purposes.
>> 586
>> 587
>> 588 What: /sys/block/<disk>/queue/throttle_sample_time
>> 589 Date: March 2017
>> 590 Contact: linux-block@vger.kernel.org
>> 591 Description:
>> 592 [RW] This is the time window that blk-throttle samples data, in
>> 593 millisecond. blk-throttle makes decision based on the
>> 594 samplings. Lower time means cgroups have more smooth throughput,
>> 595 but higher CPU overhead. This exists only when
>> 596 CONFIG_BLK_DEV_THROTTLING_LOW is enabled.
>> 597
649 598
650 What: /sys/block/<disk>/queue/virt_b 599 What: /sys/block/<disk>/queue/virt_boundary_mask
651 Date: April 2021 600 Date: April 2021
652 Contact: linux-block@vger.kernel.org 601 Contact: linux-block@vger.kernel.org
653 Description: 602 Description:
654 [RO] This file shows the I/O s 603 [RO] This file shows the I/O segment memory alignment mask for
655 the block device. I/O request 604 the block device. I/O requests to this device will be split
656 between segments wherever eith 605 between segments wherever either the memory address of the end
657 of the previous segment or the 606 of the previous segment or the memory address of the beginning
658 of the current segment is not 607 of the current segment is not aligned to virt_boundary_mask + 1
659 bytes. 608 bytes.
660 609
661 610
662 What: /sys/block/<disk>/queue/wbt_la 611 What: /sys/block/<disk>/queue/wbt_lat_usec
663 Date: November 2016 612 Date: November 2016
664 Contact: linux-block@vger.kernel.org 613 Contact: linux-block@vger.kernel.org
665 Description: 614 Description:
666 [RW] If the device is register 615 [RW] If the device is registered for writeback throttling, then
667 this file shows the target min 616 this file shows the target minimum read latency. If this latency
668 is exceeded in a given window 617 is exceeded in a given window of time (see wb_window_usec), then
669 the writeback throttling will 618 the writeback throttling will start scaling back writes. Writing
670 a value of '0' to this file di 619 a value of '0' to this file disables the feature. Writing a
671 value of '-1' to this file res 620 value of '-1' to this file resets the value to the default
672 setting. 621 setting.
673 622
674 623
675 What: /sys/block/<disk>/queue/write_ 624 What: /sys/block/<disk>/queue/write_cache
676 Date: April 2016 625 Date: April 2016
677 Contact: linux-block@vger.kernel.org 626 Contact: linux-block@vger.kernel.org
678 Description: 627 Description:
679 [RW] When read, this file will 628 [RW] When read, this file will display whether the device has
680 write back caching enabled or 629 write back caching enabled or not. It will return "write back"
681 for the former case, and "writ 630 for the former case, and "write through" for the latter. Writing
682 to this file can change the ke 631 to this file can change the kernels view of the device, but it
683 doesn't alter the device state 632 doesn't alter the device state. This means that it might not be
684 safe to toggle the setting fro 633 safe to toggle the setting from "write back" to "write through",
685 since that will also eliminate 634 since that will also eliminate cache flushes issued by the
686 kernel. 635 kernel.
687 636
688 637
689 What: /sys/block/<disk>/queue/write_ 638 What: /sys/block/<disk>/queue/write_same_max_bytes
690 Date: January 2012 639 Date: January 2012
691 Contact: Martin K. Petersen <martin.pete 640 Contact: Martin K. Petersen <martin.petersen@oracle.com>
692 Description: 641 Description:
693 [RO] Some devices support a wr 642 [RO] Some devices support a write same operation in which a
694 single data block can be writt 643 single data block can be written to a range of several
695 contiguous blocks on storage. 644 contiguous blocks on storage. This can be used to wipe areas on
696 disk or to initialize drives i 645 disk or to initialize drives in a RAID configuration.
697 write_same_max_bytes indicates 646 write_same_max_bytes indicates how many bytes can be written in
698 a single write same command. I 647 a single write same command. If write_same_max_bytes is 0, write
699 same is not supported by the d 648 same is not supported by the device.
700 649
701 650
702 What: /sys/block/<disk>/queue/write_ 651 What: /sys/block/<disk>/queue/write_zeroes_max_bytes
703 Date: November 2016 652 Date: November 2016
704 Contact: Chaitanya Kulkarni <chaitanya.k 653 Contact: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
705 Description: 654 Description:
706 [RO] Devices that support writ 655 [RO] Devices that support write zeroes operation in which a
707 single request can be issued t 656 single request can be issued to zero out the range of contiguous
708 blocks on storage without havi 657 blocks on storage without having any payload in the request.
709 This can be used to optimize w 658 This can be used to optimize writing zeroes to the devices.
710 write_zeroes_max_bytes indicat 659 write_zeroes_max_bytes indicates how many bytes can be written
711 in a single write zeroes comma 660 in a single write zeroes command. If write_zeroes_max_bytes is
712 0, write zeroes is not support 661 0, write zeroes is not supported by the device.
713 662
714 663
715 What: /sys/block/<disk>/queue/zone_a 664 What: /sys/block/<disk>/queue/zone_append_max_bytes
716 Date: May 2020 665 Date: May 2020
717 Contact: linux-block@vger.kernel.org 666 Contact: linux-block@vger.kernel.org
718 Description: 667 Description:
719 [RO] This is the maximum numbe 668 [RO] This is the maximum number of bytes that can be written to
720 a sequential zone of a zoned b 669 a sequential zone of a zoned block device using a zone append
721 write operation (REQ_OP_ZONE_A 670 write operation (REQ_OP_ZONE_APPEND). This value is always 0 for
722 regular block devices. 671 regular block devices.
723 672
724 673
725 What: /sys/block/<disk>/queue/zone_w 674 What: /sys/block/<disk>/queue/zone_write_granularity
726 Date: January 2021 675 Date: January 2021
727 Contact: linux-block@vger.kernel.org 676 Contact: linux-block@vger.kernel.org
728 Description: 677 Description:
729 [RO] This indicates the alignm 678 [RO] This indicates the alignment constraint, in bytes, for
730 write operations in sequential 679 write operations in sequential zones of zoned block devices
731 (devices with a zoned attribut 680 (devices with a zoned attributed that reports "host-managed" or
732 "host-aware"). This value is a 681 "host-aware"). This value is always 0 for regular block devices.
733 682
734 683
735 What: /sys/block/<disk>/queue/zoned 684 What: /sys/block/<disk>/queue/zoned
736 Date: September 2016 685 Date: September 2016
737 Contact: Damien Le Moal <damien.lemoal@w 686 Contact: Damien Le Moal <damien.lemoal@wdc.com>
738 Description: 687 Description:
739 [RO] zoned indicates if the de 688 [RO] zoned indicates if the device is a zoned block device and
740 the zone model of the device i 689 the zone model of the device if it is indeed zoned. The
741 possible values indicated by z 690 possible values indicated by zoned are "none" for regular block
742 devices and "host-aware" or "h 691 devices and "host-aware" or "host-managed" for zoned block
743 devices. The characteristics o 692 devices. The characteristics of host-aware and host-managed
744 zoned block devices are descri 693 zoned block devices are described in the ZBC (Zoned Block
745 Commands) and ZAC (Zoned Devic 694 Commands) and ZAC (Zoned Device ATA Command Set) standards.
746 These standards also define th 695 These standards also define the "drive-managed" zone model.
747 However, since drive-managed z 696 However, since drive-managed zoned block devices do not support
748 zone commands, they will be tr 697 zone commands, they will be treated as regular block devices and
749 zoned will report "none". 698 zoned will report "none".
750 699
751 700
752 What: /sys/block/<disk>/hidden 701 What: /sys/block/<disk>/hidden
753 Date: March 2023 702 Date: March 2023
754 Contact: linux-block@vger.kernel.org 703 Contact: linux-block@vger.kernel.org
755 Description: 704 Description:
756 [RO] the block device is hidde 705 [RO] the block device is hidden. it doesn’t produce events, and
757 can’t be opened from userspa 706 can’t be opened from userspace or using blkdev_get*.
758 Used for the underlying compon 707 Used for the underlying components of multipath devices.
759 708
760 709
761 What: /sys/block/<disk>/stat 710 What: /sys/block/<disk>/stat
762 Date: February 2008 711 Date: February 2008
763 Contact: Jerome Marchand <jmarchan@redha 712 Contact: Jerome Marchand <jmarchan@redhat.com>
764 Description: 713 Description:
765 The /sys/block/<disk>/stat fil 714 The /sys/block/<disk>/stat files displays the I/O
766 statistics of disk <disk>. The 715 statistics of disk <disk>. They contain 11 fields:
767 716
768 == ========================== 717 == ==============================================
769 1 reads completed successful 718 1 reads completed successfully
770 2 reads merged 719 2 reads merged
771 3 sectors read 720 3 sectors read
772 4 time spent reading (ms) 721 4 time spent reading (ms)
773 5 writes completed 722 5 writes completed
774 6 writes merged 723 6 writes merged
775 7 sectors written 724 7 sectors written
776 8 time spent writing (ms) 725 8 time spent writing (ms)
777 9 I/Os currently in progress 726 9 I/Os currently in progress
778 10 time spent doing I/Os (ms) 727 10 time spent doing I/Os (ms)
779 11 weighted time spent doing 728 11 weighted time spent doing I/Os (ms)
780 12 discards completed 729 12 discards completed
781 13 discards merged 730 13 discards merged
782 14 sectors discarded 731 14 sectors discarded
783 15 time spent discarding (ms) 732 15 time spent discarding (ms)
784 16 flush requests completed 733 16 flush requests completed
785 17 time spent flushing (ms) 734 17 time spent flushing (ms)
786 == ========================== 735 == ==============================================
787 736
788 For more details refer Documen 737 For more details refer Documentation/admin-guide/iostats.rst
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