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Disk plugin
Type: read
Callbacks: config, init, read
Status: supported
First version: 1.5
Copyright: 2005–2008 Florian octo Forster
2009 Manuel Sanmartin
License: GPLv2
Manpage: collectd.conf(5)
List of Plugins

The Disk plugin collects performance statistics of hard-disks and, where supported, partitions. While the “octets” and “operations” are quite straight forward, the other two datasets need a little explanation:

  • “merged” are the number of operations, that could be merged into other, already queued operations, i. e. one physical disk access served two or more logical operations. Of course, the higher that number, the better.
  • “time” is the average time an I/O-operation took to complete. Since this is a little messy to calculate take the actual values with a grain of salt.

Since 5.5 there are also additional metrics on the Linux platform:

  • “io_time” - time spent doing I/Os (ms). You can treat this metric as a device load percentage (Value of 1 sec time spent matches 100% of load).
  • “weighted_io_time” - measure of both I/O completion time and the backlog that may be accumulating.
  • “pending_operations” - shows queue size of pending I/O operations.

For details about these metrics you can also read kernel documentation (Explanations of fields "Field 9", "Field 10" and "Field 11").


<Plugin "disk">
  Disk "sda"
  Disk "/^hd/"
  IgnoreSelected false

Example graphs






Plugin-disk-pending operations.png


  • Linux
    • Either /proc/diskstats (Linux 2.6) or /proc/partitions (Linux 2.4)
  • Darwin / Mac OS X
  • Solaris
    • libkstat(3KSTAT)
  • AIX
    • libperfstat(3)
  • FreeBSD