| 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. |