Synnefo » snf-ganeti

Diskstats collector

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This storage data collector will gather information about the status of the

disks installed in the system, as listed in the /proc/diskstats file. This means

that not only physical hard drives, but also ramdisks and loopback devices will

be listed.

Its ``kind`` in the report will be ``0`` (`Performance reporting collectors`_).

Its ``category`` field in the report will contain the value ``storage``.

When executed in verbose mode, the ``data`` section of the report of this

collector will be a list of items, each representing one disk, each providing

the following fields:

``major``

  The major number of the device.

``minor``

  The minor number of the device.

``name``

  The name of the device.

``reads``

  This is the total number of reads completed successfully.

``mergedReads``

  Reads which are adjacent to each other may be merged for efficiency. Thus

  two 4K reads may become one 8K read before it is ultimately handed to the

  disk, and so it will be counted (and queued) as only one I/O. This field

  specifies how often this was done.

``secRead``

  This is the total number of sectors read successfully.

``timeRead``

  This is the total number of milliseconds spent by all reads.

``writes``

  This is the total number of writes completed successfully.

``mergedWrites``

  Writes which are adjacent to each other may be merged for efficiency. Thus

  two 4K writes may become one 8K read before it is ultimately handed to the

  disk, and so it will be counted (and queued) as only one I/O. This field

  specifies how often this was done.

``secWritten``

  This is the total number of sectors written successfully.

``timeWrite``

  This is the total number of milliseconds spent by all writes

``ios``

  The number of I/Os currently in progress.

  The only field that should go to zero, it is incremented as requests are

  given to appropriate struct request_queue and decremented as they finish.

``timeIO``

  The number of milliseconds spent doing I/Os. This field increases so long

  as field ``IOs`` is nonzero.

``wIOmillis``

  The weighted number of milliseconds spent doing I/Os.

  This field is incremented at each I/O start, I/O completion, I/O merge,

  or read of these stats by the number of I/Os in progress (field ``IOs``)

  times the number of milliseconds spent doing I/O since the last update of

  this field. This can provide an easy measure of both I/O completion time

  and the backlog that may be accumulating.