block: Export I/O topology for block devices and partitions
[linux-2.6.git] / Documentation / ABI / testing / sysfs-block
1 What:           /sys/block/<disk>/stat
2 Date:           February 2008
3 Contact:        Jerome Marchand <jmarchan@redhat.com>
4 Description:
5                 The /sys/block/<disk>/stat files displays the I/O
6                 statistics of disk <disk>. They contain 11 fields:
7                  1 - reads completed succesfully
8                  2 - reads merged
9                  3 - sectors read
10                  4 - time spent reading (ms)
11                  5 - writes completed
12                  6 - writes merged
13                  7 - sectors written
14                  8 - time spent writing (ms)
15                  9 - I/Os currently in progress
16                 10 - time spent doing I/Os (ms)
17                 11 - weighted time spent doing I/Os (ms)
18                 For more details refer Documentation/iostats.txt
19
20
21 What:           /sys/block/<disk>/<part>/stat
22 Date:           February 2008
23 Contact:        Jerome Marchand <jmarchan@redhat.com>
24 Description:
25                 The /sys/block/<disk>/<part>/stat files display the
26                 I/O statistics of partition <part>. The format is the
27                 same as the above-written /sys/block/<disk>/stat
28                 format.
29
30
31 What:           /sys/block/<disk>/integrity/format
32 Date:           June 2008
33 Contact:        Martin K. Petersen <martin.petersen@oracle.com>
34 Description:
35                 Metadata format for integrity capable block device.
36                 E.g. T10-DIF-TYPE1-CRC.
37
38
39 What:           /sys/block/<disk>/integrity/read_verify
40 Date:           June 2008
41 Contact:        Martin K. Petersen <martin.petersen@oracle.com>
42 Description:
43                 Indicates whether the block layer should verify the
44                 integrity of read requests serviced by devices that
45                 support sending integrity metadata.
46
47
48 What:           /sys/block/<disk>/integrity/tag_size
49 Date:           June 2008
50 Contact:        Martin K. Petersen <martin.petersen@oracle.com>
51 Description:
52                 Number of bytes of integrity tag space available per
53                 512 bytes of data.
54
55
56 What:           /sys/block/<disk>/integrity/write_generate
57 Date:           June 2008
58 Contact:        Martin K. Petersen <martin.petersen@oracle.com>
59 Description:
60                 Indicates whether the block layer should automatically
61                 generate checksums for write requests bound for
62                 devices that support receiving integrity metadata.
63
64 What:           /sys/block/<disk>/alignment_offset
65 Date:           April 2009
66 Contact:        Martin K. Petersen <martin.petersen@oracle.com>
67 Description:
68                 Storage devices may report a physical block size that is
69                 bigger than the logical block size (for instance a drive
70                 with 4KB physical sectors exposing 512-byte logical
71                 blocks to the operating system).  This parameter
72                 indicates how many bytes the beginning of the device is
73                 offset from the disk's natural alignment.
74
75 What:           /sys/block/<disk>/<partition>/alignment_offset
76 Date:           April 2009
77 Contact:        Martin K. Petersen <martin.petersen@oracle.com>
78 Description:
79                 Storage devices may report a physical block size that is
80                 bigger than the logical block size (for instance a drive
81                 with 4KB physical sectors exposing 512-byte logical
82                 blocks to the operating system).  This parameter
83                 indicates how many bytes the beginning of the partition
84                 is offset from the disk's natural alignment.
85
86 What:           /sys/block/<disk>/queue/logical_block_size
87 Date:           May 2009
88 Contact:        Martin K. Petersen <martin.petersen@oracle.com>
89 Description:
90                 This is the smallest unit the storage device can
91                 address.  It is typically 512 bytes.
92
93 What:           /sys/block/<disk>/queue/physical_block_size
94 Date:           May 2009
95 Contact:        Martin K. Petersen <martin.petersen@oracle.com>
96 Description:
97                 This is the smallest unit the storage device can write
98                 without resorting to read-modify-write operation.  It is
99                 usually the same as the logical block size but may be
100                 bigger.  One example is SATA drives with 4KB sectors
101                 that expose a 512-byte logical block size to the
102                 operating system.
103
104 What:           /sys/block/<disk>/queue/minimum_io_size
105 Date:           April 2009
106 Contact:        Martin K. Petersen <martin.petersen@oracle.com>
107 Description:
108                 Storage devices may report a preferred minimum I/O size,
109                 which is the smallest request the device can perform
110                 without incurring a read-modify-write penalty.  For disk
111                 drives this is often the physical block size.  For RAID
112                 arrays it is often the stripe chunk size.
113
114 What:           /sys/block/<disk>/queue/optimal_io_size
115 Date:           April 2009
116 Contact:        Martin K. Petersen <martin.petersen@oracle.com>
117 Description:
118                 Storage devices may report an optimal I/O size, which is
119                 the device's preferred unit of receiving I/O.  This is
120                 rarely reported for disk drives.  For RAID devices it is
121                 usually the stripe width or the internal block size.