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To support devices with physical block sizes bigger than 512 bytes we need to ensure proper alignment. This patch adds support for exposing I/O topology characteristics as devices are stacked. logical_block_size is the smallest unit the device can address. physical_block_size indicates the smallest I/O the device can write without incurring a read-modify-write penalty. The io_min parameter is the smallest preferred I/O size reported by the device. In many cases this is the same as the physical block size. However, the io_min parameter can be scaled up when stacking (RAID5 chunk size > physical block size). The io_opt characteristic indicates the optimal I/O size reported by the device. This is usually the stripe width for arrays. The alignment_offset parameter indicates the number of bytes the start of the device/partition is offset from the device's natural alignment. Partition tools and MD/DM utilities can use this to pad their offsets so filesystems start on proper boundaries. Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
122 lines
4.1 KiB
Plaintext
122 lines
4.1 KiB
Plaintext
What: /sys/block/<disk>/stat
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Date: February 2008
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Contact: Jerome Marchand <jmarchan@redhat.com>
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Description:
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The /sys/block/<disk>/stat files displays the I/O
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statistics of disk <disk>. They contain 11 fields:
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1 - reads completed succesfully
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2 - reads merged
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3 - sectors read
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4 - time spent reading (ms)
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5 - writes completed
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6 - writes merged
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7 - sectors written
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8 - time spent writing (ms)
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9 - I/Os currently in progress
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10 - time spent doing I/Os (ms)
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11 - weighted time spent doing I/Os (ms)
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For more details refer Documentation/iostats.txt
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What: /sys/block/<disk>/<part>/stat
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Date: February 2008
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Contact: Jerome Marchand <jmarchan@redhat.com>
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Description:
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The /sys/block/<disk>/<part>/stat files display the
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I/O statistics of partition <part>. The format is the
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same as the above-written /sys/block/<disk>/stat
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format.
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What: /sys/block/<disk>/integrity/format
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Date: June 2008
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Metadata format for integrity capable block device.
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E.g. T10-DIF-TYPE1-CRC.
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What: /sys/block/<disk>/integrity/read_verify
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Date: June 2008
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Indicates whether the block layer should verify the
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integrity of read requests serviced by devices that
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support sending integrity metadata.
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What: /sys/block/<disk>/integrity/tag_size
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Date: June 2008
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Number of bytes of integrity tag space available per
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512 bytes of data.
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What: /sys/block/<disk>/integrity/write_generate
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Date: June 2008
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Indicates whether the block layer should automatically
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generate checksums for write requests bound for
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devices that support receiving integrity metadata.
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What: /sys/block/<disk>/alignment_offset
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Date: April 2009
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Storage devices may report a physical block size that is
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bigger than the logical block size (for instance a drive
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with 4KB physical sectors exposing 512-byte logical
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blocks to the operating system). This parameter
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indicates how many bytes the beginning of the device is
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offset from the disk's natural alignment.
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What: /sys/block/<disk>/<partition>/alignment_offset
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Date: April 2009
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Storage devices may report a physical block size that is
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bigger than the logical block size (for instance a drive
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with 4KB physical sectors exposing 512-byte logical
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blocks to the operating system). This parameter
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indicates how many bytes the beginning of the partition
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is offset from the disk's natural alignment.
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What: /sys/block/<disk>/queue/logical_block_size
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Date: May 2009
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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This is the smallest unit the storage device can
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address. It is typically 512 bytes.
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What: /sys/block/<disk>/queue/physical_block_size
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Date: May 2009
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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This is the smallest unit the storage device can write
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without resorting to read-modify-write operation. It is
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usually the same as the logical block size but may be
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bigger. One example is SATA drives with 4KB sectors
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that expose a 512-byte logical block size to the
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operating system.
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What: /sys/block/<disk>/queue/minimum_io_size
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Date: April 2009
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Storage devices may report a preferred minimum I/O size,
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which is the smallest request the device can perform
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without incurring a read-modify-write penalty. For disk
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drives this is often the physical block size. For RAID
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arrays it is often the stripe chunk size.
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What: /sys/block/<disk>/queue/optimal_io_size
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Date: April 2009
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Contact: Martin K. Petersen <martin.petersen@oracle.com>
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Description:
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Storage devices may report an optimal I/O size, which is
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the device's preferred unit of receiving I/O. This is
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rarely reported for disk drives. For RAID devices it is
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usually the stripe width or the internal block size.
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