Proc filesystem - diskstats

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The /proc/diskstats file displays the I/O statistics of block devices.

Here we have a system which has one disk sda used by Linux operating system and two disks sdb sdc for other purpose.

$ cat /etc/centos-release
CentOS Linux release 7.9.2009 (Core)

$ uname -r
3.10.0-1160.11.1.el7.x86_64

$ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0   128G  0 disk
├─sda1   8:1    0   3.7G  0 part /boot
└─sda2   8:2    0 124.3G  0 part /
sdb      8:16   0    60G  0 disk
sdc      8:32   0    60G  0 disk

The following is the content of /proc/diskstats file.

$ cat /proc/diskstats
   8       0 sda 20076 3 798556 75864 23573766 4732398 253002144 24887356 0 9814563 24947775
   8       1 sda1 143 0 22434 681 44 21 21664 588 0 397 1269
   8       2 sda2 19905 3 774042 75034 23573722 4732377 252980480 24886768 0 9814404 24946360
   8      32 sdc 88 0 4160 4 0 0 0 0 0 4 4
   8      16 sdb 88 0 4160 2 0 0 0 0 0 2 2

Taking the sda line for example, the following explains the meaning of each column.

  • 8 - major number
  • 0 - minor number
  • sda - device name
  • 20076 - reads completed successfully
  • 3 - reads merged
  • 798556 - sectors read
  • 75864 - time spent reading (ms)
  • 23573766 - writes completed
  • 4732398 - writes merged
  • 253002144 - sectors written
  • 24887356 - time spent writing (ms)
  • 0 - I/Os currently in progress
  • 9814563 - time spent doing I/Os (ms)
  • 24947775 - weighted time spent doing I/Os (ms)

You may see more columns from the /proc/diskstats file if the kernel version is 4.18+ or 5.5+. For the detailed explanation, please refer to the documentation.