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