107c9093cSEric BiggersWhat: /sys/block/<disk>/alignment_offset 207c9093cSEric BiggersDate: April 2009 307c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 407c9093cSEric BiggersDescription: 507c9093cSEric Biggers Storage devices may report a physical block size that is 607c9093cSEric Biggers bigger than the logical block size (for instance a drive 707c9093cSEric Biggers with 4KB physical sectors exposing 512-byte logical 807c9093cSEric Biggers blocks to the operating system). This parameter 907c9093cSEric Biggers indicates how many bytes the beginning of the device is 1007c9093cSEric Biggers offset from the disk's natural alignment. 1107c9093cSEric Biggers 1207c9093cSEric Biggers 1307c9093cSEric BiggersWhat: /sys/block/<disk>/discard_alignment 1407c9093cSEric BiggersDate: May 2011 1507c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 1607c9093cSEric BiggersDescription: 1707c9093cSEric Biggers Devices that support discard functionality may 1807c9093cSEric Biggers internally allocate space in units that are bigger than 1907c9093cSEric Biggers the exported logical block size. The discard_alignment 2007c9093cSEric Biggers parameter indicates how many bytes the beginning of the 2107c9093cSEric Biggers device is offset from the internal allocation unit's 2207c9093cSEric Biggers natural alignment. 2307c9093cSEric Biggers 2407c9093cSEric Biggers 2507c9093cSEric BiggersWhat: /sys/block/<disk>/diskseq 2607c9093cSEric BiggersDate: February 2021 2707c9093cSEric BiggersContact: Matteo Croce <mcroce@microsoft.com> 2807c9093cSEric BiggersDescription: 2907c9093cSEric Biggers The /sys/block/<disk>/diskseq files reports the disk 3007c9093cSEric Biggers sequence number, which is a monotonically increasing 3107c9093cSEric Biggers number assigned to every drive. 3207c9093cSEric Biggers Some devices, like the loop device, refresh such number 3307c9093cSEric Biggers every time the backing file is changed. 3407c9093cSEric Biggers The value type is 64 bit unsigned. 3507c9093cSEric Biggers 3607c9093cSEric Biggers 3707c9093cSEric BiggersWhat: /sys/block/<disk>/inflight 3807c9093cSEric BiggersDate: October 2009 3907c9093cSEric BiggersContact: Jens Axboe <axboe@kernel.dk>, Nikanth Karthikesan <knikanth@suse.de> 4007c9093cSEric BiggersDescription: 4107c9093cSEric Biggers Reports the number of I/O requests currently in progress 4207c9093cSEric Biggers (pending / in flight) in a device driver. This can be less 4307c9093cSEric Biggers than the number of requests queued in the block device queue. 4407c9093cSEric Biggers The report contains 2 fields: one for read requests 4507c9093cSEric Biggers and one for write requests. 4607c9093cSEric Biggers The value type is unsigned int. 4707c9093cSEric Biggers Cf. Documentation/block/stat.rst which contains a single value for 4807c9093cSEric Biggers requests in flight. 49849ab826SEric Biggers This is related to /sys/block/<disk>/queue/nr_requests 5007c9093cSEric Biggers and for SCSI device also its queue_depth. 5107c9093cSEric Biggers 5207c9093cSEric Biggers 5307c9093cSEric BiggersWhat: /sys/block/<disk>/integrity/device_is_integrity_capable 5407c9093cSEric BiggersDate: July 2014 5507c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 5607c9093cSEric BiggersDescription: 5707c9093cSEric Biggers Indicates whether a storage device is capable of storing 5807c9093cSEric Biggers integrity metadata. Set if the device is T10 PI-capable. 5907c9093cSEric Biggers 6007c9093cSEric Biggers 6107c9093cSEric BiggersWhat: /sys/block/<disk>/integrity/format 6207c9093cSEric BiggersDate: June 2008 6307c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 6407c9093cSEric BiggersDescription: 6507c9093cSEric Biggers Metadata format for integrity capable block device. 6607c9093cSEric Biggers E.g. T10-DIF-TYPE1-CRC. 6707c9093cSEric Biggers 6807c9093cSEric Biggers 6907c9093cSEric BiggersWhat: /sys/block/<disk>/integrity/protection_interval_bytes 7007c9093cSEric BiggersDate: July 2015 7107c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 7207c9093cSEric BiggersDescription: 7307c9093cSEric Biggers Describes the number of data bytes which are protected 7407c9093cSEric Biggers by one integrity tuple. Typically the device's logical 7507c9093cSEric Biggers block size. 7607c9093cSEric Biggers 7707c9093cSEric Biggers 7807c9093cSEric BiggersWhat: /sys/block/<disk>/integrity/read_verify 7907c9093cSEric BiggersDate: June 2008 8007c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 8107c9093cSEric BiggersDescription: 8207c9093cSEric Biggers Indicates whether the block layer should verify the 8307c9093cSEric Biggers integrity of read requests serviced by devices that 8407c9093cSEric Biggers support sending integrity metadata. 8507c9093cSEric Biggers 8607c9093cSEric Biggers 8707c9093cSEric BiggersWhat: /sys/block/<disk>/integrity/tag_size 8807c9093cSEric BiggersDate: June 2008 8907c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 9007c9093cSEric BiggersDescription: 9107c9093cSEric Biggers Number of bytes of integrity tag space available per 9207c9093cSEric Biggers 512 bytes of data. 9307c9093cSEric Biggers 9407c9093cSEric Biggers 9507c9093cSEric BiggersWhat: /sys/block/<disk>/integrity/write_generate 9607c9093cSEric BiggersDate: June 2008 9707c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 9807c9093cSEric BiggersDescription: 9907c9093cSEric Biggers Indicates whether the block layer should automatically 10007c9093cSEric Biggers generate checksums for write requests bound for 10107c9093cSEric Biggers devices that support receiving integrity metadata. 10207c9093cSEric Biggers 10307c9093cSEric Biggers 104*a4217c67SChristoph HellwigWhat: /sys/block/<disk>/partscan 105*a4217c67SChristoph HellwigDate: May 2024 106*a4217c67SChristoph HellwigContact: Christoph Hellwig <hch@lst.de> 107*a4217c67SChristoph HellwigDescription: 108*a4217c67SChristoph Hellwig The /sys/block/<disk>/partscan files reports if partition 109*a4217c67SChristoph Hellwig scanning is enabled for the disk. It returns "1" if partition 110*a4217c67SChristoph Hellwig scanning is enabled, or "0" if not. The value type is a 32-bit 111*a4217c67SChristoph Hellwig unsigned integer, but only "0" and "1" are valid values. 112*a4217c67SChristoph Hellwig 113*a4217c67SChristoph Hellwig 11407c9093cSEric BiggersWhat: /sys/block/<disk>/<partition>/alignment_offset 11507c9093cSEric BiggersDate: April 2009 11607c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 11707c9093cSEric BiggersDescription: 11807c9093cSEric Biggers Storage devices may report a physical block size that is 11907c9093cSEric Biggers bigger than the logical block size (for instance a drive 12007c9093cSEric Biggers with 4KB physical sectors exposing 512-byte logical 12107c9093cSEric Biggers blocks to the operating system). This parameter 12207c9093cSEric Biggers indicates how many bytes the beginning of the partition 12307c9093cSEric Biggers is offset from the disk's natural alignment. 12407c9093cSEric Biggers 12507c9093cSEric Biggers 12607c9093cSEric BiggersWhat: /sys/block/<disk>/<partition>/discard_alignment 12707c9093cSEric BiggersDate: May 2011 12807c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 12907c9093cSEric BiggersDescription: 13007c9093cSEric Biggers Devices that support discard functionality may 13107c9093cSEric Biggers internally allocate space in units that are bigger than 13207c9093cSEric Biggers the exported logical block size. The discard_alignment 13307c9093cSEric Biggers parameter indicates how many bytes the beginning of the 13407c9093cSEric Biggers partition is offset from the internal allocation unit's 13507c9093cSEric Biggers natural alignment. 13607c9093cSEric Biggers 13707c9093cSEric Biggers 13807c9093cSEric BiggersWhat: /sys/block/<disk>/<partition>/stat 13907c9093cSEric BiggersDate: February 2008 14007c9093cSEric BiggersContact: Jerome Marchand <jmarchan@redhat.com> 14107c9093cSEric BiggersDescription: 14207c9093cSEric Biggers The /sys/block/<disk>/<partition>/stat files display the 14307c9093cSEric Biggers I/O statistics of partition <partition>. The format is the 14407c9093cSEric Biggers same as the format of /sys/block/<disk>/stat. 14507c9093cSEric Biggers 14607c9093cSEric Biggers 147849ab826SEric BiggersWhat: /sys/block/<disk>/queue/add_random 148849ab826SEric BiggersDate: June 2010 149849ab826SEric BiggersContact: linux-block@vger.kernel.org 150849ab826SEric BiggersDescription: 151849ab826SEric Biggers [RW] This file allows to turn off the disk entropy contribution. 152849ab826SEric Biggers Default value of this file is '1'(on). 153849ab826SEric Biggers 154849ab826SEric Biggers 15507c9093cSEric BiggersWhat: /sys/block/<disk>/queue/chunk_sectors 15607c9093cSEric BiggersDate: September 2016 15707c9093cSEric BiggersContact: Hannes Reinecke <hare@suse.com> 15807c9093cSEric BiggersDescription: 159849ab826SEric Biggers [RO] chunk_sectors has different meaning depending on the type 16007c9093cSEric Biggers of the disk. For a RAID device (dm-raid), chunk_sectors 161849ab826SEric Biggers indicates the size in 512B sectors of the RAID volume stripe 162849ab826SEric Biggers segment. For a zoned block device, either host-aware or 163849ab826SEric Biggers host-managed, chunk_sectors indicates the size in 512B sectors 164849ab826SEric Biggers of the zones of the device, with the eventual exception of the 165849ab826SEric Biggers last zone of the device which may be smaller. 166849ab826SEric Biggers 167849ab826SEric Biggers 16820f01f16SEric BiggersWhat: /sys/block/<disk>/queue/crypto/ 16920f01f16SEric BiggersDate: February 2022 17020f01f16SEric BiggersContact: linux-block@vger.kernel.org 17120f01f16SEric BiggersDescription: 17220f01f16SEric Biggers The presence of this subdirectory of /sys/block/<disk>/queue/ 17320f01f16SEric Biggers indicates that the device supports inline encryption. This 17420f01f16SEric Biggers subdirectory contains files which describe the inline encryption 17520f01f16SEric Biggers capabilities of the device. For more information about inline 17620f01f16SEric Biggers encryption, refer to Documentation/block/inline-encryption.rst. 17720f01f16SEric Biggers 17820f01f16SEric Biggers 17920f01f16SEric BiggersWhat: /sys/block/<disk>/queue/crypto/max_dun_bits 18020f01f16SEric BiggersDate: February 2022 18120f01f16SEric BiggersContact: linux-block@vger.kernel.org 18220f01f16SEric BiggersDescription: 18320f01f16SEric Biggers [RO] This file shows the maximum length, in bits, of data unit 18420f01f16SEric Biggers numbers accepted by the device in inline encryption requests. 18520f01f16SEric Biggers 18620f01f16SEric Biggers 18720f01f16SEric BiggersWhat: /sys/block/<disk>/queue/crypto/modes/<mode> 18820f01f16SEric BiggersDate: February 2022 18920f01f16SEric BiggersContact: linux-block@vger.kernel.org 19020f01f16SEric BiggersDescription: 19120f01f16SEric Biggers [RO] For each crypto mode (i.e., encryption/decryption 19220f01f16SEric Biggers algorithm) the device supports with inline encryption, a file 19320f01f16SEric Biggers will exist at this location. It will contain a hexadecimal 19420f01f16SEric Biggers number that is a bitmask of the supported data unit sizes, in 19520f01f16SEric Biggers bytes, for that crypto mode. 19620f01f16SEric Biggers 19720f01f16SEric Biggers Currently, the crypto modes that may be supported are: 19820f01f16SEric Biggers 19920f01f16SEric Biggers * AES-256-XTS 20020f01f16SEric Biggers * AES-128-CBC-ESSIV 20120f01f16SEric Biggers * Adiantum 20220f01f16SEric Biggers 20320f01f16SEric Biggers For example, if a device supports AES-256-XTS inline encryption 20420f01f16SEric Biggers with data unit sizes of 512 and 4096 bytes, the file 20520f01f16SEric Biggers /sys/block/<disk>/queue/crypto/modes/AES-256-XTS will exist and 20620f01f16SEric Biggers will contain "0x1200". 20720f01f16SEric Biggers 20820f01f16SEric Biggers 20920f01f16SEric BiggersWhat: /sys/block/<disk>/queue/crypto/num_keyslots 21020f01f16SEric BiggersDate: February 2022 21120f01f16SEric BiggersContact: linux-block@vger.kernel.org 21220f01f16SEric BiggersDescription: 21320f01f16SEric Biggers [RO] This file shows the number of keyslots the device has for 21420f01f16SEric Biggers use with inline encryption. 21520f01f16SEric Biggers 21620f01f16SEric Biggers 217849ab826SEric BiggersWhat: /sys/block/<disk>/queue/dax 218849ab826SEric BiggersDate: June 2016 219849ab826SEric BiggersContact: linux-block@vger.kernel.org 220849ab826SEric BiggersDescription: 221849ab826SEric Biggers [RO] This file indicates whether the device supports Direct 222849ab826SEric Biggers Access (DAX), used by CPU-addressable storage to bypass the 223849ab826SEric Biggers pagecache. It shows '1' if true, '0' if not. 22407c9093cSEric Biggers 22507c9093cSEric Biggers 22607c9093cSEric BiggersWhat: /sys/block/<disk>/queue/discard_granularity 22707c9093cSEric BiggersDate: May 2011 22807c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 22907c9093cSEric BiggersDescription: 230849ab826SEric Biggers [RO] Devices that support discard functionality may internally 231849ab826SEric Biggers allocate space using units that are bigger than the logical 232849ab826SEric Biggers block size. The discard_granularity parameter indicates the size 233849ab826SEric Biggers of the internal allocation unit in bytes if reported by the 234849ab826SEric Biggers device. Otherwise the discard_granularity will be set to match 235849ab826SEric Biggers the device's physical block size. A discard_granularity of 0 236849ab826SEric Biggers means that the device does not support discard functionality. 23707c9093cSEric Biggers 23807c9093cSEric Biggers 23907c9093cSEric BiggersWhat: /sys/block/<disk>/queue/discard_max_bytes 24007c9093cSEric BiggersDate: May 2011 24107c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 24207c9093cSEric BiggersDescription: 243849ab826SEric Biggers [RW] While discard_max_hw_bytes is the hardware limit for the 244849ab826SEric Biggers device, this setting is the software limit. Some devices exhibit 245849ab826SEric Biggers large latencies when large discards are issued, setting this 246849ab826SEric Biggers value lower will make Linux issue smaller discards and 247849ab826SEric Biggers potentially help reduce latencies induced by large discard 248849ab826SEric Biggers operations. 249849ab826SEric Biggers 250849ab826SEric Biggers 251849ab826SEric BiggersWhat: /sys/block/<disk>/queue/discard_max_hw_bytes 252849ab826SEric BiggersDate: July 2015 253849ab826SEric BiggersContact: linux-block@vger.kernel.org 254849ab826SEric BiggersDescription: 255849ab826SEric Biggers [RO] Devices that support discard functionality may have 256849ab826SEric Biggers internal limits on the number of bytes that can be trimmed or 257849ab826SEric Biggers unmapped in a single operation. The `discard_max_hw_bytes` 258849ab826SEric Biggers parameter is set by the device driver to the maximum number of 259849ab826SEric Biggers bytes that can be discarded in a single operation. Discard 260849ab826SEric Biggers requests issued to the device must not exceed this limit. A 261849ab826SEric Biggers `discard_max_hw_bytes` value of 0 means that the device does not 262849ab826SEric Biggers support discard functionality. 26307c9093cSEric Biggers 26407c9093cSEric Biggers 26507c9093cSEric BiggersWhat: /sys/block/<disk>/queue/discard_zeroes_data 26607c9093cSEric BiggersDate: May 2011 26707c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 26807c9093cSEric BiggersDescription: 269849ab826SEric Biggers [RO] Will always return 0. Don't rely on any specific behavior 27007c9093cSEric Biggers for discards, and don't read this file. 27107c9093cSEric Biggers 27207c9093cSEric Biggers 2733850e13fSKeith BuschWhat: /sys/block/<disk>/queue/dma_alignment 2743850e13fSKeith BuschDate: May 2022 2753850e13fSKeith BuschContact: linux-block@vger.kernel.org 2763850e13fSKeith BuschDescription: 2773850e13fSKeith Busch Reports the alignment that user space addresses must have to be 2783850e13fSKeith Busch used for raw block device access with O_DIRECT and other driver 2793850e13fSKeith Busch specific passthrough mechanisms. 2803850e13fSKeith Busch 2813850e13fSKeith Busch 282849ab826SEric BiggersWhat: /sys/block/<disk>/queue/fua 283849ab826SEric BiggersDate: May 2018 284849ab826SEric BiggersContact: linux-block@vger.kernel.org 285849ab826SEric BiggersDescription: 286849ab826SEric Biggers [RO] Whether or not the block driver supports the FUA flag for 287849ab826SEric Biggers write requests. FUA stands for Force Unit Access. If the FUA 288849ab826SEric Biggers flag is set that means that write requests must bypass the 289849ab826SEric Biggers volatile cache of the storage device. 290849ab826SEric Biggers 291849ab826SEric Biggers 292849ab826SEric BiggersWhat: /sys/block/<disk>/queue/hw_sector_size 293849ab826SEric BiggersDate: January 2008 294849ab826SEric BiggersContact: linux-block@vger.kernel.org 295849ab826SEric BiggersDescription: 296849ab826SEric Biggers [RO] This is the hardware sector size of the device, in bytes. 297849ab826SEric Biggers 298849ab826SEric Biggers 299849ab826SEric BiggersWhat: /sys/block/<disk>/queue/independent_access_ranges/ 300849ab826SEric BiggersDate: October 2021 301849ab826SEric BiggersContact: linux-block@vger.kernel.org 302849ab826SEric BiggersDescription: 303849ab826SEric Biggers [RO] The presence of this sub-directory of the 304849ab826SEric Biggers /sys/block/xxx/queue/ directory indicates that the device is 305849ab826SEric Biggers capable of executing requests targeting different sector ranges 306849ab826SEric Biggers in parallel. For instance, single LUN multi-actuator hard-disks 307849ab826SEric Biggers will have an independent_access_ranges directory if the device 308ebab9426SBjorn Helgaas correctly advertises the sector ranges of its actuators. 309849ab826SEric Biggers 310849ab826SEric Biggers The independent_access_ranges directory contains one directory 311849ab826SEric Biggers per access range, with each range described using the sector 312849ab826SEric Biggers (RO) attribute file to indicate the first sector of the range 313849ab826SEric Biggers and the nr_sectors (RO) attribute file to indicate the total 314849ab826SEric Biggers number of sectors in the range starting from the first sector of 315849ab826SEric Biggers the range. For example, a dual-actuator hard-disk will have the 316849ab826SEric Biggers following independent_access_ranges entries.:: 317849ab826SEric Biggers 318849ab826SEric Biggers $ tree /sys/block/<disk>/queue/independent_access_ranges/ 319849ab826SEric Biggers /sys/block/<disk>/queue/independent_access_ranges/ 320849ab826SEric Biggers |-- 0 321849ab826SEric Biggers | |-- nr_sectors 322849ab826SEric Biggers | `-- sector 323849ab826SEric Biggers `-- 1 324849ab826SEric Biggers |-- nr_sectors 325849ab826SEric Biggers `-- sector 326849ab826SEric Biggers 327849ab826SEric Biggers The sector and nr_sectors attributes use 512B sector unit, 328849ab826SEric Biggers regardless of the actual block size of the device. Independent 329849ab826SEric Biggers access ranges do not overlap and include all sectors within the 330849ab826SEric Biggers device capacity. The access ranges are numbered in increasing 331849ab826SEric Biggers order of the range start sector, that is, the sector attribute 332849ab826SEric Biggers of range 0 always has the value 0. 333849ab826SEric Biggers 334849ab826SEric Biggers 335849ab826SEric BiggersWhat: /sys/block/<disk>/queue/io_poll 336849ab826SEric BiggersDate: November 2015 337849ab826SEric BiggersContact: linux-block@vger.kernel.org 338849ab826SEric BiggersDescription: 339849ab826SEric Biggers [RW] When read, this file shows whether polling is enabled (1) 340849ab826SEric Biggers or disabled (0). Writing '0' to this file will disable polling 341849ab826SEric Biggers for this device. Writing any non-zero value will enable this 342849ab826SEric Biggers feature. 343849ab826SEric Biggers 344849ab826SEric Biggers 345849ab826SEric BiggersWhat: /sys/block/<disk>/queue/io_poll_delay 346849ab826SEric BiggersDate: November 2016 347849ab826SEric BiggersContact: linux-block@vger.kernel.org 348849ab826SEric BiggersDescription: 34954bdd67dSKeith Busch [RW] This was used to control what kind of polling will be 35054bdd67dSKeith Busch performed. It is now fixed to -1, which is classic polling. 351849ab826SEric Biggers In this mode, the CPU will repeatedly ask for completions 35254bdd67dSKeith Busch without giving up any time. 35354bdd67dSKeith Busch <deprecated> 354849ab826SEric Biggers 355849ab826SEric Biggers 35607c9093cSEric BiggersWhat: /sys/block/<disk>/queue/io_timeout 35707c9093cSEric BiggersDate: November 2018 35807c9093cSEric BiggersContact: Weiping Zhang <zhangweiping@didiglobal.com> 35907c9093cSEric BiggersDescription: 360849ab826SEric Biggers [RW] io_timeout is the request timeout in milliseconds. If a 361849ab826SEric Biggers request does not complete in this time then the block driver 362849ab826SEric Biggers timeout handler is invoked. That timeout handler can decide to 363849ab826SEric Biggers retry the request, to fail it or to start a device recovery 364849ab826SEric Biggers strategy. 365849ab826SEric Biggers 366849ab826SEric Biggers 367849ab826SEric BiggersWhat: /sys/block/<disk>/queue/iostats 368849ab826SEric BiggersDate: January 2009 369849ab826SEric BiggersContact: linux-block@vger.kernel.org 370849ab826SEric BiggersDescription: 371849ab826SEric Biggers [RW] This file is used to control (on/off) the iostats 372849ab826SEric Biggers accounting of the disk. 37307c9093cSEric Biggers 37407c9093cSEric Biggers 37507c9093cSEric BiggersWhat: /sys/block/<disk>/queue/logical_block_size 37607c9093cSEric BiggersDate: May 2009 37707c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 37807c9093cSEric BiggersDescription: 379849ab826SEric Biggers [RO] This is the smallest unit the storage device can address. 380849ab826SEric Biggers It is typically 512 bytes. 38107c9093cSEric Biggers 38207c9093cSEric Biggers 38307c9093cSEric BiggersWhat: /sys/block/<disk>/queue/max_active_zones 38407c9093cSEric BiggersDate: July 2020 38507c9093cSEric BiggersContact: Niklas Cassel <niklas.cassel@wdc.com> 38607c9093cSEric BiggersDescription: 387849ab826SEric Biggers [RO] For zoned block devices (zoned attribute indicating 38807c9093cSEric Biggers "host-managed" or "host-aware"), the sum of zones belonging to 38907c9093cSEric Biggers any of the zone states: EXPLICIT OPEN, IMPLICIT OPEN or CLOSED, 39007c9093cSEric Biggers is limited by this value. If this value is 0, there is no limit. 39107c9093cSEric Biggers 392849ab826SEric Biggers If the host attempts to exceed this limit, the driver should 393849ab826SEric Biggers report this error with BLK_STS_ZONE_ACTIVE_RESOURCE, which user 394849ab826SEric Biggers space may see as the EOVERFLOW errno. 395849ab826SEric Biggers 396849ab826SEric Biggers 397849ab826SEric BiggersWhat: /sys/block/<disk>/queue/max_discard_segments 398849ab826SEric BiggersDate: February 2017 399849ab826SEric BiggersContact: linux-block@vger.kernel.org 400849ab826SEric BiggersDescription: 401849ab826SEric Biggers [RO] The maximum number of DMA scatter/gather entries in a 402849ab826SEric Biggers discard request. 403849ab826SEric Biggers 404849ab826SEric Biggers 405849ab826SEric BiggersWhat: /sys/block/<disk>/queue/max_hw_sectors_kb 406849ab826SEric BiggersDate: September 2004 407849ab826SEric BiggersContact: linux-block@vger.kernel.org 408849ab826SEric BiggersDescription: 409849ab826SEric Biggers [RO] This is the maximum number of kilobytes supported in a 410849ab826SEric Biggers single data transfer. 411849ab826SEric Biggers 412849ab826SEric Biggers 413849ab826SEric BiggersWhat: /sys/block/<disk>/queue/max_integrity_segments 414849ab826SEric BiggersDate: September 2010 415849ab826SEric BiggersContact: linux-block@vger.kernel.org 416849ab826SEric BiggersDescription: 417849ab826SEric Biggers [RO] Maximum number of elements in a DMA scatter/gather list 418849ab826SEric Biggers with integrity data that will be submitted by the block layer 419849ab826SEric Biggers core to the associated block driver. 420849ab826SEric Biggers 42107c9093cSEric Biggers 42207c9093cSEric BiggersWhat: /sys/block/<disk>/queue/max_open_zones 42307c9093cSEric BiggersDate: July 2020 42407c9093cSEric BiggersContact: Niklas Cassel <niklas.cassel@wdc.com> 42507c9093cSEric BiggersDescription: 426849ab826SEric Biggers [RO] For zoned block devices (zoned attribute indicating 42707c9093cSEric Biggers "host-managed" or "host-aware"), the sum of zones belonging to 428849ab826SEric Biggers any of the zone states: EXPLICIT OPEN or IMPLICIT OPEN, is 429849ab826SEric Biggers limited by this value. If this value is 0, there is no limit. 430849ab826SEric Biggers 431849ab826SEric Biggers 432849ab826SEric BiggersWhat: /sys/block/<disk>/queue/max_sectors_kb 433849ab826SEric BiggersDate: September 2004 434849ab826SEric BiggersContact: linux-block@vger.kernel.org 435849ab826SEric BiggersDescription: 436849ab826SEric Biggers [RW] This is the maximum number of kilobytes that the block 437849ab826SEric Biggers layer will allow for a filesystem request. Must be smaller than 438c9c77418SKeith Busch or equal to the maximum size allowed by the hardware. Write 0 439c9c77418SKeith Busch to use default kernel settings. 440849ab826SEric Biggers 441849ab826SEric Biggers 442849ab826SEric BiggersWhat: /sys/block/<disk>/queue/max_segment_size 443849ab826SEric BiggersDate: March 2010 444849ab826SEric BiggersContact: linux-block@vger.kernel.org 445849ab826SEric BiggersDescription: 446849ab826SEric Biggers [RO] Maximum size in bytes of a single element in a DMA 447849ab826SEric Biggers scatter/gather list. 448849ab826SEric Biggers 449849ab826SEric Biggers 450849ab826SEric BiggersWhat: /sys/block/<disk>/queue/max_segments 451849ab826SEric BiggersDate: March 2010 452849ab826SEric BiggersContact: linux-block@vger.kernel.org 453849ab826SEric BiggersDescription: 454849ab826SEric Biggers [RO] Maximum number of elements in a DMA scatter/gather list 455849ab826SEric Biggers that is submitted to the associated block driver. 45607c9093cSEric Biggers 45707c9093cSEric Biggers 45807c9093cSEric BiggersWhat: /sys/block/<disk>/queue/minimum_io_size 45907c9093cSEric BiggersDate: April 2009 46007c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 46107c9093cSEric BiggersDescription: 462849ab826SEric Biggers [RO] Storage devices may report a granularity or preferred 463849ab826SEric Biggers minimum I/O size which is the smallest request the device can 464849ab826SEric Biggers perform without incurring a performance penalty. For disk 465849ab826SEric Biggers drives this is often the physical block size. For RAID arrays 466849ab826SEric Biggers it is often the stripe chunk size. A properly aligned multiple 467849ab826SEric Biggers of minimum_io_size is the preferred request size for workloads 468849ab826SEric Biggers where a high number of I/O operations is desired. 46907c9093cSEric Biggers 47007c9093cSEric Biggers 47107c9093cSEric BiggersWhat: /sys/block/<disk>/queue/nomerges 47207c9093cSEric BiggersDate: January 2010 4738b0551a7SEric BiggersContact: linux-block@vger.kernel.org 47407c9093cSEric BiggersDescription: 475849ab826SEric Biggers [RW] Standard I/O elevator operations include attempts to merge 476849ab826SEric Biggers contiguous I/Os. For known random I/O loads these attempts will 477849ab826SEric Biggers always fail and result in extra cycles being spent in the 478849ab826SEric Biggers kernel. This allows one to turn off this behavior on one of two 479849ab826SEric Biggers ways: When set to 1, complex merge checks are disabled, but the 480849ab826SEric Biggers simple one-shot merges with the previous I/O request are 481849ab826SEric Biggers enabled. When set to 2, all merge tries are disabled. The 482849ab826SEric Biggers default value is 0 - which enables all types of merge tries. 483849ab826SEric Biggers 484849ab826SEric Biggers 485849ab826SEric BiggersWhat: /sys/block/<disk>/queue/nr_requests 486849ab826SEric BiggersDate: July 2003 487849ab826SEric BiggersContact: linux-block@vger.kernel.org 488849ab826SEric BiggersDescription: 489849ab826SEric Biggers [RW] This controls how many requests may be allocated in the 490849ab826SEric Biggers block layer for read or write requests. Note that the total 491849ab826SEric Biggers allocated number may be twice this amount, since it applies only 492849ab826SEric Biggers to reads or writes (not the accumulated sum). 493849ab826SEric Biggers 494849ab826SEric Biggers To avoid priority inversion through request starvation, a 495849ab826SEric Biggers request queue maintains a separate request pool per each cgroup 496849ab826SEric Biggers when CONFIG_BLK_CGROUP is enabled, and this parameter applies to 497849ab826SEric Biggers each such per-block-cgroup request pool. IOW, if there are N 498849ab826SEric Biggers block cgroups, each request queue may have up to N request 499849ab826SEric Biggers pools, each independently regulated by nr_requests. 50007c9093cSEric Biggers 50107c9093cSEric Biggers 50207c9093cSEric BiggersWhat: /sys/block/<disk>/queue/nr_zones 50307c9093cSEric BiggersDate: November 2018 50407c9093cSEric BiggersContact: Damien Le Moal <damien.lemoal@wdc.com> 50507c9093cSEric BiggersDescription: 506849ab826SEric Biggers [RO] nr_zones indicates the total number of zones of a zoned 507849ab826SEric Biggers block device ("host-aware" or "host-managed" zone model). For 508849ab826SEric Biggers regular block devices, the value is always 0. 50907c9093cSEric Biggers 51007c9093cSEric Biggers 51107c9093cSEric BiggersWhat: /sys/block/<disk>/queue/optimal_io_size 51207c9093cSEric BiggersDate: April 2009 51307c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 51407c9093cSEric BiggersDescription: 515849ab826SEric Biggers [RO] Storage devices may report an optimal I/O size, which is 516849ab826SEric Biggers the device's preferred unit for sustained I/O. This is rarely 517849ab826SEric Biggers reported for disk drives. For RAID arrays it is usually the 518849ab826SEric Biggers stripe width or the internal track size. A properly aligned 519849ab826SEric Biggers multiple of optimal_io_size is the preferred request size for 520849ab826SEric Biggers workloads where sustained throughput is desired. If no optimal 521849ab826SEric Biggers I/O size is reported this file contains 0. 52207c9093cSEric Biggers 52307c9093cSEric Biggers 52407c9093cSEric BiggersWhat: /sys/block/<disk>/queue/physical_block_size 52507c9093cSEric BiggersDate: May 2009 52607c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 52707c9093cSEric BiggersDescription: 528849ab826SEric Biggers [RO] This is the smallest unit a physical storage device can 529849ab826SEric Biggers write atomically. It is usually the same as the logical block 530849ab826SEric Biggers size but may be bigger. One example is SATA drives with 4KB 531849ab826SEric Biggers sectors that expose a 512-byte logical block size to the 532849ab826SEric Biggers operating system. For stacked block devices the 533849ab826SEric Biggers physical_block_size variable contains the maximum 534849ab826SEric Biggers physical_block_size of the component devices. 535849ab826SEric Biggers 536849ab826SEric Biggers 537849ab826SEric BiggersWhat: /sys/block/<disk>/queue/read_ahead_kb 538849ab826SEric BiggersDate: May 2004 539849ab826SEric BiggersContact: linux-block@vger.kernel.org 540849ab826SEric BiggersDescription: 541849ab826SEric Biggers [RW] Maximum number of kilobytes to read-ahead for filesystems 542849ab826SEric Biggers on this block device. 543849ab826SEric Biggers 544849ab826SEric Biggers 545849ab826SEric BiggersWhat: /sys/block/<disk>/queue/rotational 546849ab826SEric BiggersDate: January 2009 547849ab826SEric BiggersContact: linux-block@vger.kernel.org 548849ab826SEric BiggersDescription: 549849ab826SEric Biggers [RW] This file is used to stat if the device is of rotational 550849ab826SEric Biggers type or non-rotational type. 551849ab826SEric Biggers 552849ab826SEric Biggers 553849ab826SEric BiggersWhat: /sys/block/<disk>/queue/rq_affinity 554849ab826SEric BiggersDate: September 2008 555849ab826SEric BiggersContact: linux-block@vger.kernel.org 556849ab826SEric BiggersDescription: 557849ab826SEric Biggers [RW] If this option is '1', the block layer will migrate request 558849ab826SEric Biggers completions to the cpu "group" that originally submitted the 559849ab826SEric Biggers request. For some workloads this provides a significant 560849ab826SEric Biggers reduction in CPU cycles due to caching effects. 561849ab826SEric Biggers 562849ab826SEric Biggers For storage configurations that need to maximize distribution of 563849ab826SEric Biggers completion processing setting this option to '2' forces the 564849ab826SEric Biggers completion to run on the requesting cpu (bypassing the "group" 565849ab826SEric Biggers aggregation logic). 566849ab826SEric Biggers 567849ab826SEric Biggers 568849ab826SEric BiggersWhat: /sys/block/<disk>/queue/scheduler 569849ab826SEric BiggersDate: October 2004 570849ab826SEric BiggersContact: linux-block@vger.kernel.org 571849ab826SEric BiggersDescription: 572849ab826SEric Biggers [RW] When read, this file will display the current and available 573849ab826SEric Biggers IO schedulers for this block device. The currently active IO 574849ab826SEric Biggers scheduler will be enclosed in [] brackets. Writing an IO 575849ab826SEric Biggers scheduler name to this file will switch control of this block 576849ab826SEric Biggers device to that new IO scheduler. Note that writing an IO 577849ab826SEric Biggers scheduler name to this file will attempt to load that IO 578849ab826SEric Biggers scheduler module, if it isn't already present in the system. 579849ab826SEric Biggers 580849ab826SEric Biggers 58111630104SEric BiggersWhat: /sys/block/<disk>/queue/stable_writes 58211630104SEric BiggersDate: September 2020 58311630104SEric BiggersContact: linux-block@vger.kernel.org 58411630104SEric BiggersDescription: 58511630104SEric Biggers [RW] This file will contain '1' if memory must not be modified 58611630104SEric Biggers while it is being used in a write request to this device. When 58711630104SEric Biggers this is the case and the kernel is performing writeback of a 58811630104SEric Biggers page, the kernel will wait for writeback to complete before 58911630104SEric Biggers allowing the page to be modified again, rather than allowing 59011630104SEric Biggers immediate modification as is normally the case. This 59111630104SEric Biggers restriction arises when the device accesses the memory multiple 59211630104SEric Biggers times where the same data must be seen every time -- for 59311630104SEric Biggers example, once to calculate a checksum and once to actually write 59411630104SEric Biggers the data. If no such restriction exists, this file will contain 59511630104SEric Biggers '0'. This file is writable for testing purposes. 59611630104SEric Biggers 5978bc2f7c6SEric BiggersWhat: /sys/block/<disk>/queue/virt_boundary_mask 5988bc2f7c6SEric BiggersDate: April 2021 5998bc2f7c6SEric BiggersContact: linux-block@vger.kernel.org 6008bc2f7c6SEric BiggersDescription: 6018bc2f7c6SEric Biggers [RO] This file shows the I/O segment memory alignment mask for 6028bc2f7c6SEric Biggers the block device. I/O requests to this device will be split 6038bc2f7c6SEric Biggers between segments wherever either the memory address of the end 6048bc2f7c6SEric Biggers of the previous segment or the memory address of the beginning 6058bc2f7c6SEric Biggers of the current segment is not aligned to virt_boundary_mask + 1 6068bc2f7c6SEric Biggers bytes. 6078bc2f7c6SEric Biggers 6088bc2f7c6SEric Biggers 609849ab826SEric BiggersWhat: /sys/block/<disk>/queue/wbt_lat_usec 610849ab826SEric BiggersDate: November 2016 611849ab826SEric BiggersContact: linux-block@vger.kernel.org 612849ab826SEric BiggersDescription: 613849ab826SEric Biggers [RW] If the device is registered for writeback throttling, then 614849ab826SEric Biggers this file shows the target minimum read latency. If this latency 615849ab826SEric Biggers is exceeded in a given window of time (see wb_window_usec), then 616849ab826SEric Biggers the writeback throttling will start scaling back writes. Writing 617849ab826SEric Biggers a value of '0' to this file disables the feature. Writing a 618849ab826SEric Biggers value of '-1' to this file resets the value to the default 619849ab826SEric Biggers setting. 620849ab826SEric Biggers 621849ab826SEric Biggers 622849ab826SEric BiggersWhat: /sys/block/<disk>/queue/write_cache 623849ab826SEric BiggersDate: April 2016 624849ab826SEric BiggersContact: linux-block@vger.kernel.org 625849ab826SEric BiggersDescription: 626849ab826SEric Biggers [RW] When read, this file will display whether the device has 627849ab826SEric Biggers write back caching enabled or not. It will return "write back" 628849ab826SEric Biggers for the former case, and "write through" for the latter. Writing 629849ab826SEric Biggers to this file can change the kernels view of the device, but it 630849ab826SEric Biggers doesn't alter the device state. This means that it might not be 631849ab826SEric Biggers safe to toggle the setting from "write back" to "write through", 632849ab826SEric Biggers since that will also eliminate cache flushes issued by the 633849ab826SEric Biggers kernel. 63407c9093cSEric Biggers 63507c9093cSEric Biggers 63607c9093cSEric BiggersWhat: /sys/block/<disk>/queue/write_same_max_bytes 63707c9093cSEric BiggersDate: January 2012 63807c9093cSEric BiggersContact: Martin K. Petersen <martin.petersen@oracle.com> 63907c9093cSEric BiggersDescription: 640849ab826SEric Biggers [RO] Some devices support a write same operation in which a 64107c9093cSEric Biggers single data block can be written to a range of several 642849ab826SEric Biggers contiguous blocks on storage. This can be used to wipe areas on 643849ab826SEric Biggers disk or to initialize drives in a RAID configuration. 644849ab826SEric Biggers write_same_max_bytes indicates how many bytes can be written in 645849ab826SEric Biggers a single write same command. If write_same_max_bytes is 0, write 646849ab826SEric Biggers same is not supported by the device. 64707c9093cSEric Biggers 64807c9093cSEric Biggers 64907c9093cSEric BiggersWhat: /sys/block/<disk>/queue/write_zeroes_max_bytes 65007c9093cSEric BiggersDate: November 2016 65107c9093cSEric BiggersContact: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> 65207c9093cSEric BiggersDescription: 653849ab826SEric Biggers [RO] Devices that support write zeroes operation in which a 654849ab826SEric Biggers single request can be issued to zero out the range of contiguous 655849ab826SEric Biggers blocks on storage without having any payload in the request. 656849ab826SEric Biggers This can be used to optimize writing zeroes to the devices. 657849ab826SEric Biggers write_zeroes_max_bytes indicates how many bytes can be written 658849ab826SEric Biggers in a single write zeroes command. If write_zeroes_max_bytes is 659849ab826SEric Biggers 0, write zeroes is not supported by the device. 660849ab826SEric Biggers 661849ab826SEric Biggers 662849ab826SEric BiggersWhat: /sys/block/<disk>/queue/zone_append_max_bytes 663849ab826SEric BiggersDate: May 2020 664849ab826SEric BiggersContact: linux-block@vger.kernel.org 665849ab826SEric BiggersDescription: 666849ab826SEric Biggers [RO] This is the maximum number of bytes that can be written to 667849ab826SEric Biggers a sequential zone of a zoned block device using a zone append 668849ab826SEric Biggers write operation (REQ_OP_ZONE_APPEND). This value is always 0 for 669849ab826SEric Biggers regular block devices. 670849ab826SEric Biggers 671849ab826SEric Biggers 672849ab826SEric BiggersWhat: /sys/block/<disk>/queue/zone_write_granularity 673849ab826SEric BiggersDate: January 2021 674849ab826SEric BiggersContact: linux-block@vger.kernel.org 675849ab826SEric BiggersDescription: 676849ab826SEric Biggers [RO] This indicates the alignment constraint, in bytes, for 677849ab826SEric Biggers write operations in sequential zones of zoned block devices 678849ab826SEric Biggers (devices with a zoned attributed that reports "host-managed" or 679849ab826SEric Biggers "host-aware"). This value is always 0 for regular block devices. 68007c9093cSEric Biggers 68107c9093cSEric Biggers 68207c9093cSEric BiggersWhat: /sys/block/<disk>/queue/zoned 68307c9093cSEric BiggersDate: September 2016 68407c9093cSEric BiggersContact: Damien Le Moal <damien.lemoal@wdc.com> 68507c9093cSEric BiggersDescription: 686849ab826SEric Biggers [RO] zoned indicates if the device is a zoned block device and 687849ab826SEric Biggers the zone model of the device if it is indeed zoned. The 688849ab826SEric Biggers possible values indicated by zoned are "none" for regular block 689849ab826SEric Biggers devices and "host-aware" or "host-managed" for zoned block 690849ab826SEric Biggers devices. The characteristics of host-aware and host-managed 691849ab826SEric Biggers zoned block devices are described in the ZBC (Zoned Block 692849ab826SEric Biggers Commands) and ZAC (Zoned Device ATA Command Set) standards. 693849ab826SEric Biggers These standards also define the "drive-managed" zone model. 694849ab826SEric Biggers However, since drive-managed zoned block devices do not support 695849ab826SEric Biggers zone commands, they will be treated as regular block devices and 696849ab826SEric Biggers zoned will report "none". 69707c9093cSEric Biggers 69807c9093cSEric Biggers 699e3306221SSagi GrimbergWhat: /sys/block/<disk>/hidden 700e3306221SSagi GrimbergDate: March 2023 701e3306221SSagi GrimbergContact: linux-block@vger.kernel.org 702e3306221SSagi GrimbergDescription: 703e3306221SSagi Grimberg [RO] the block device is hidden. it doesn’t produce events, and 704e3306221SSagi Grimberg can’t be opened from userspace or using blkdev_get*. 705e3306221SSagi Grimberg Used for the underlying components of multipath devices. 706e3306221SSagi Grimberg 707e3306221SSagi Grimberg 708ae7a7a53SEric BiggersWhat: /sys/block/<disk>/stat 709ae7a7a53SEric BiggersDate: February 2008 710ae7a7a53SEric BiggersContact: Jerome Marchand <jmarchan@redhat.com> 711ae7a7a53SEric BiggersDescription: 712ae7a7a53SEric Biggers The /sys/block/<disk>/stat files displays the I/O 713ae7a7a53SEric Biggers statistics of disk <disk>. They contain 11 fields: 714ae7a7a53SEric Biggers 715ae7a7a53SEric Biggers == ============================================== 716ae7a7a53SEric Biggers 1 reads completed successfully 717ae7a7a53SEric Biggers 2 reads merged 718ae7a7a53SEric Biggers 3 sectors read 719ae7a7a53SEric Biggers 4 time spent reading (ms) 720ae7a7a53SEric Biggers 5 writes completed 721ae7a7a53SEric Biggers 6 writes merged 722ae7a7a53SEric Biggers 7 sectors written 723ae7a7a53SEric Biggers 8 time spent writing (ms) 724ae7a7a53SEric Biggers 9 I/Os currently in progress 725ae7a7a53SEric Biggers 10 time spent doing I/Os (ms) 726ae7a7a53SEric Biggers 11 weighted time spent doing I/Os (ms) 727ae7a7a53SEric Biggers 12 discards completed 728ae7a7a53SEric Biggers 13 discards merged 729ae7a7a53SEric Biggers 14 sectors discarded 730ae7a7a53SEric Biggers 15 time spent discarding (ms) 731ae7a7a53SEric Biggers 16 flush requests completed 732ae7a7a53SEric Biggers 17 time spent flushing (ms) 733ae7a7a53SEric Biggers == ============================================== 734ae7a7a53SEric Biggers 735ae7a7a53SEric Biggers For more details refer Documentation/admin-guide/iostats.rst 736