| What: /sys/block/<disk>/stat |
| Date: February 2008 |
| Contact: Jerome Marchand <jmarchan@redhat.com> |
| Description: |
| The /sys/block/<disk>/stat files displays the I/O |
| statistics of disk <disk>. They contain 11 fields: |
| 1 - reads completed successfully |
| 2 - reads merged |
| 3 - sectors read |
| 4 - time spent reading (ms) |
| 5 - writes completed |
| 6 - writes merged |
| 7 - sectors written |
| 8 - time spent writing (ms) |
| 9 - I/Os currently in progress |
| 10 - time spent doing I/Os (ms) |
| 11 - weighted time spent doing I/Os (ms) |
| For more details refer Documentation/iostats.txt |
| |
| |
| What: /sys/block/<disk>/<part>/stat |
| Date: February 2008 |
| Contact: Jerome Marchand <jmarchan@redhat.com> |
| Description: |
| The /sys/block/<disk>/<part>/stat files display the |
| I/O statistics of partition <part>. The format is the |
| same as the above-written /sys/block/<disk>/stat |
| format. |
| |
| |
| What: /sys/block/<disk>/integrity/format |
| Date: June 2008 |
| Contact: Martin K. Petersen <martin.petersen@oracle.com> |
| Description: |
| Metadata format for integrity capable block device. |
| E.g. T10-DIF-TYPE1-CRC. |
| |
| |
| What: /sys/block/<disk>/integrity/read_verify |
| Date: June 2008 |
| Contact: Martin K. Petersen <martin.petersen@oracle.com> |
| Description: |
| Indicates whether the block layer should verify the |
| integrity of read requests serviced by devices that |
| support sending integrity metadata. |
| |
| |
| What: /sys/block/<disk>/integrity/tag_size |
| Date: June 2008 |
| Contact: Martin K. Petersen <martin.petersen@oracle.com> |
| Description: |
| Number of bytes of integrity tag space available per |
| 512 bytes of data. |
| |
| |
| What: /sys/block/<disk>/integrity/write_generate |
| Date: June 2008 |
| Contact: Martin K. Petersen <martin.petersen@oracle.com> |
| Description: |
| Indicates whether the block layer should automatically |
| generate checksums for write requests bound for |
| devices that support receiving integrity metadata. |
| |
| What: /sys/block/<disk>/alignment_offset |
| Date: April 2009 |
| Contact: Martin K. Petersen <martin.petersen@oracle.com> |
| Description: |
| Storage devices may report a physical block size that is |
| bigger than the logical block size (for instance a drive |
| with 4KB physical sectors exposing 512-byte logical |
| blocks to the operating system). This parameter |
| indicates how many bytes the beginning of the device is |
| offset from the disk's natural alignment. |
| |
| What: /sys/block/<disk>/<partition>/alignment_offset |
| Date: April 2009 |
| Contact: Martin K. Petersen <martin.petersen@oracle.com> |
| Description: |
| Storage devices may report a physical block size that is |
| bigger than the logical block size (for instance a drive |
| with 4KB physical sectors exposing 512-byte logical |
| blocks to the operating system). This parameter |
| indicates how many bytes the beginning of the partition |
| is offset from the disk's natural alignment. |
| |
| What: /sys/block/<disk>/queue/logical_block_size |
| Date: May 2009 |
| Contact: Martin K. Petersen <martin.petersen@oracle.com> |
| Description: |
| This is the smallest unit the storage device can |
| address. It is typically 512 bytes. |
| |
| What: /sys/block/<disk>/queue/physical_block_size |
| Date: May 2009 |
| Contact: Martin K. Petersen <martin.petersen@oracle.com> |
| Description: |
| This is the smallest unit a physical storage device can |
| write atomically. It is usually the same as the logical |
| block size but may be bigger. One example is SATA |
| drives with 4KB sectors that expose a 512-byte logical |
| block size to the operating system. For stacked block |
| devices the physical_block_size variable contains the |
| maximum physical_block_size of the component devices. |
| |
| What: /sys/block/<disk>/queue/minimum_io_size |
| Date: April 2009 |
| Contact: Martin K. Petersen <martin.petersen@oracle.com> |
| Description: |
| Storage devices may report a granularity or preferred |
| minimum I/O size which is the smallest request the |
| device can perform without incurring a performance |
| penalty. For disk drives this is often the physical |
| block size. For RAID arrays it is often the stripe |
| chunk size. A properly aligned multiple of |
| minimum_io_size is the preferred request size for |
| workloads where a high number of I/O operations is |
| desired. |
| |
| What: /sys/block/<disk>/queue/optimal_io_size |
| Date: April 2009 |
| Contact: Martin K. Petersen <martin.petersen@oracle.com> |
| Description: |
| Storage devices may report an optimal I/O size, which is |
| the device's preferred unit for sustained I/O. This is |
| rarely reported for disk drives. For RAID arrays it is |
| usually the stripe width or the internal track size. A |
| properly aligned multiple of optimal_io_size is the |
| preferred request size for workloads where sustained |
| throughput is desired. If no optimal I/O size is |
| reported this file contains 0. |
| |
| What: /sys/block/<disk>/queue/nomerges |
| Date: January 2010 |
| Contact: |
| Description: |
| Standard I/O elevator operations include attempts to |
| merge contiguous I/Os. For known random I/O loads these |
| attempts will always fail and result in extra cycles |
| being spent in the kernel. This allows one to turn off |
| this behavior on one of two ways: When set to 1, complex |
| merge checks are disabled, but the simple one-shot merges |
| with the previous I/O request are enabled. When set to 2, |
| all merge tries are disabled. The default value is 0 - |
| which enables all types of merge tries. |
| |
| What: /sys/block/<disk>/discard_alignment |
| Date: May 2011 |
| Contact: Martin K. Petersen <martin.petersen@oracle.com> |
| Description: |
| Devices that support discard functionality may |
| internally allocate space in units that are bigger than |
| the exported logical block size. The discard_alignment |
| parameter indicates how many bytes the beginning of the |
| device is offset from the internal allocation unit's |
| natural alignment. |
| |
| What: /sys/block/<disk>/<partition>/discard_alignment |
| Date: May 2011 |
| Contact: Martin K. Petersen <martin.petersen@oracle.com> |
| Description: |
| Devices that support discard functionality may |
| internally allocate space in units that are bigger than |
| the exported logical block size. The discard_alignment |
| parameter indicates how many bytes the beginning of the |
| partition is offset from the internal allocation unit's |
| natural alignment. |
| |
| What: /sys/block/<disk>/queue/discard_granularity |
| Date: May 2011 |
| Contact: Martin K. Petersen <martin.petersen@oracle.com> |
| Description: |
| Devices that support discard functionality may |
| internally allocate space using units that are bigger |
| than the logical block size. The discard_granularity |
| parameter indicates the size of the internal allocation |
| unit in bytes if reported by the device. Otherwise the |
| discard_granularity will be set to match the device's |
| physical block size. A discard_granularity of 0 means |
| that the device does not support discard functionality. |
| |
| What: /sys/block/<disk>/queue/discard_max_bytes |
| Date: May 2011 |
| Contact: Martin K. Petersen <martin.petersen@oracle.com> |
| Description: |
| Devices that support discard functionality may have |
| internal limits on the number of bytes that can be |
| trimmed or unmapped in a single operation. Some storage |
| protocols also have inherent limits on the number of |
| blocks that can be described in a single command. The |
| discard_max_bytes parameter is set by the device driver |
| to the maximum number of bytes that can be discarded in |
| a single operation. Discard requests issued to the |
| device must not exceed this limit. A discard_max_bytes |
| value of 0 means that the device does not support |
| discard functionality. |
| |
| What: /sys/block/<disk>/queue/discard_zeroes_data |
| Date: May 2011 |
| Contact: Martin K. Petersen <martin.petersen@oracle.com> |
| Description: |
| Devices that support discard functionality may return |
| stale or random data when a previously discarded block |
| is read back. This can cause problems if the filesystem |
| expects discarded blocks to be explicitly cleared. If a |
| device reports that it deterministically returns zeroes |
| when a discarded area is read the discard_zeroes_data |
| parameter will be set to one. Otherwise it will be 0 and |
| the result of reading a discarded area is undefined. |
| What: /sys/block/<disk>/alias |
| Date: Aug 2011 |
| Contact: Nao Nishijima <nao.nishijima.xt@hitachi.com> |
| Description: |
| A raw device name of a disk does not always point a same disk |
| each boot-up time. Therefore, users have to use persistent |
| device names, which udev creates when the kernel finds a disk, |
| instead of raw device name. However, kernel doesn't show those |
| persistent names on its messages (e.g. dmesg). |
| This file can store an alias of the disk and it would be |
| appeared in kernel messages if it is set. A disk can have an |
| alias which length is up to 255bytes. Users can use alphabets, |
| numbers, "-" and "_" in alias name. This file is writeonce. |
