Documentation/admin-guide/iostats.rst

5 The kernel exposes disk statistics via ``/proc/diskstats`` and
9 Here are examples using a disk with two partitions::
40 system-wide stats you'll have to find all the devices and sum them all up.
42 Field  1 -- # of reads completed (unsigned long)
45 Field  2 -- # of reads merged, field 6 -- # of writes merged (unsigned long)
48     ultimately handed to the disk, and so it will be counted (and queued)
51 Field  3 -- # of sectors read (unsigned long)
54 Field  4 -- # of milliseconds spent reading (unsigned int)
58 Field  5 -- # of writes completed (unsigned long)
61 Field  6 -- # of writes merged  (unsigned long)
64 Field  7 -- # of sectors written (unsigned long)
67 Field  8 -- # of milliseconds spent writing (unsigned int)
71 Field  9 -- # of I/Os currently in progress (unsigned int)
75 Field 10 -- # of milliseconds spent doing I/Os (unsigned int)
82 Field 11 -- weighted # of milliseconds spent doing I/Os (unsigned int)
89 Field 12 -- # of discards completed (unsigned long)
92 Field 13 -- # of discards merged (unsigned long)
95 Field 14 -- # of sectors discarded (unsigned long)
98 Field 15 -- # of milliseconds spent discarding (unsigned int)
102 Field 16 -- # of flush requests completed
106     This counts flush requests executed by disk. Not tracked for partitions.
108 Field 17 -- # of milliseconds spent flushing
118 almost a non-issue.  When the statistics are read, the per-CPU counters
121 user interface for accessing the per-CPU counters themselves.
127 -------------------
131 a disk address relative to a partition to the disk address relative to
132 the host disk happens much earlier.  All merges and timings now happen
133 at the disk level rather than at both the disk and partition level as
138 Field  1 -- # of reads issued
141 Field  2 -- # of sectors read
145 Field  3 -- # of writes issued
148 Field  4 -- # of sectors written
152 Note that since the address is translated to a disk-relative one, and no
153 record of the partition-relative address is kept, the subsequent success
166 disk and partition statistics are consistent again. Since we still don't
167 keep record of the partition-relative address, an operation is attributed to
173 ----------------
176 Linux hasn't added it already, here's the line you'll want to add to
182 In 2.6+, all disk statistics were removed from ``/proc/stat``.  In 2.4, they
187 -- ricklind@us.ibm.com