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DiskIO Input Plugin

The diskio input plugin gathers metrics about disk traffic and timing.

Configuration:

# Read metrics about disk IO by device
[[inputs.diskio]]
  ## By default, telegraf will gather stats for all devices including
  ## disk partitions.
  ## Setting devices will restrict the stats to the specified devices.
  # devices = ["sda", "sdb"]
  ## Uncomment the following line if you need disk serial numbers.
  # skip_serial_number = false
  #
  ## On systems which support it, device metadata can be added in the form of
  ## tags.
  ## Currently only Linux is supported via udev properties. You can view
  ## available properties for a device by running:
  ## 'udevadm info -q property -n /dev/sda'
  # device_tags = ["ID_FS_TYPE", "ID_FS_USAGE"]
  #
  ## Using the same metadata source as device_tags, you can also customize the
  ## name of the device via templates.
  ## The 'name_templates' parameter is a list of templates to try and apply to
  ## the device. The template may contain variables in the form of '$PROPERTY' or
  ## '${PROPERTY}'. The first template which does not contain any variables not
  ## present for the device is used as the device name tag.
  ## The typical use case is for LVM volumes, to get the VG/LV name instead of
  ## the near-meaningless DM-0 name.
  # name_templates = ["$ID_FS_LABEL","$DM_VG_NAME/$DM_LV_NAME"]

Docker container

To monitor the Docker engine host from within a container you will need to mount the host's filesystem into the container and set the HOST_PROC environment variable to the location of the /proc filesystem. Additionally, it is required to use privileged mode to provide access to /dev.

If you are using the device_tags or name_templates options, you will need to bind mount /run/udev into the container.

docker run --privileged -v /:/hostfs:ro -v /run/udev:/run/udev:ro -e HOST_PROC=/hostfs/proc telegraf

Metrics:

  • diskio
    • tags:
      • name (device name)
      • serial (device serial number)
    • fields:
      • reads (integer, counter)
      • writes (integer, counter)
      • read_bytes (integer, counter, bytes)
      • write_bytes (integer, counter, bytes)
      • read_time (integer, counter, milliseconds)
      • write_time (integer, counter, milliseconds)
      • io_time (integer, counter, milliseconds)
      • weighted_io_time (integer, counter, milliseconds)
      • iops_in_progress (integer, gauge)

On linux these values correspond to the values in /proc/diskstats and /sys/block/<dev>/stat.

reads & writes:

These values increment when an I/O request completes.

read_bytes & write_bytes:

These values count the number of bytes read from or written to this block device.

read_time & write_time:

These values count the number of milliseconds that I/O requests have waited on this block device. If there are multiple I/O requests waiting, these values will increase at a rate greater than 1000/second; for example, if 60 read requests wait for an average of 30 ms, the read_time field will increase by 60*30 = 1800.

io_time:

This value counts the number of milliseconds during which the device has had I/O requests queued.

weighted_io_time:

This value counts the number of milliseconds that I/O requests have waited on this block device. If there are multiple I/O requests waiting, this value will increase as the product of the number of milliseconds times the number of requests waiting (see read_time above for an example).

iops_in_progress:

This value counts the number of I/O requests that have been issued to the device driver but have not yet completed. It does not include I/O requests that are in the queue but not yet issued to the device driver.

Sample Queries:

Calculate percent IO utilization per disk and host:

SELECT non_negative_derivative(last("io_time"),1ms) FROM "diskio" WHERE time > now() - 30m GROUP BY "host","name",time(60s)

Calculate average queue depth:

iops_in_progress will give you an instantaneous value. This will give you the average between polling intervals.

SELECT non_negative_derivative(last("weighted_io_time",1ms)) from "diskio" WHERE time > now() - 30m GROUP BY "host","name",time(60s)

Example Output:

diskio,name=sda weighted_io_time=8411917i,read_time=7446444i,write_time=971489i,io_time=866197i,write_bytes=5397686272i,iops_in_progress=0i,reads=2970519i,writes=361139i,read_bytes=119528903168i 1502467254359000000
diskio,name=sda1 reads=2149i,read_bytes=10753536i,write_bytes=20697088i,write_time=346i,weighted_io_time=505i,writes=2110i,read_time=161i,io_time=208i,iops_in_progress=0i 1502467254359000000
diskio,name=sda2 reads=2968279i,writes=359029i,write_bytes=5376989184i,iops_in_progress=0i,weighted_io_time=8411250i,read_bytes=119517334528i,read_time=7446249i,write_time=971143i,io_time=866010i 1502467254359000000
diskio,name=sdb writes=99391856i,write_time=466700894i,io_time=630259874i,weighted_io_time=4245949844i,reads=2750773828i,read_bytes=80667939499008i,write_bytes=6329347096576i,read_time=3783042534i,iops_in_progress=2i 1502467254359000000
diskio,name=centos/root read_time=7472461i,write_time=950014i,iops_in_progress=0i,weighted_io_time=8424447i,writes=298543i,read_bytes=119510105088i,io_time=837421i,reads=2971769i,write_bytes=5192795648i 1502467254359000000
diskio,name=centos/var_log reads=1065i,writes=69711i,read_time=1083i,write_time=35376i,read_bytes=6828032i,write_bytes=184193536i,io_time=29699i,iops_in_progress=0i,weighted_io_time=36460i 1502467254359000000
diskio,name=postgresql/pgsql write_time=478267417i,io_time=631098730i,iops_in_progress=2i,weighted_io_time=4263637564i,reads=2750777151i,writes=110044361i,read_bytes=80667939288064i,write_bytes=6329347096576i,read_time=3784499336i 1502467254359000000