| 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. |
