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telegraf/plugins/inputs/system/DISK_README.md

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Disk Input Plugin

The disk input plugin gathers metrics about disk usage.

Note that used_percent is calculated by doing used / (used + free), not used / total, which is how the unix df command does it. See https://en.wikipedia.org/wiki/Df_(Unix) for more details.

Configuration:

# Read metrics about disk usage by mount point
[[inputs.disk]]
  # By default, telegraf gather stats for all mountpoints.
  # Setting mountpoints will restrict the stats to the specified mountpoints.
  # mount_points = ["/"]

Additionally, the behavior of resolving the mount_points can be configured by using the HOST_MOUNT_PREFIX environment variable. When present, this variable is prepended to the mountpoints discovered by the plugin before retrieving stats. The prefix is stripped from the reported path in the measurement. This settings is useful when running telegraf inside a docker container to report host machine metrics. In this case, the host's root volume should be mounted into the container and the HOST_MOUNT_PREFIX and HOST_ETC environment variables set.

docker run -v /:/hostfs:ro -e HOST_MOUNT_PREFIX=/hostfs -e HOST_ETC=/hostfs/etc telegraf-docker

Measurements & Fields:

  • disk
    • free (integer, bytes)
    • total (integer, bytes)
    • used (integer, bytes)
    • used_percent (float, percent)
    • inodes_free (integer, files)
    • inodes_total (integer, files)
    • inodes_used (integer, files)

Tags:

  • All measurements have the following tags:
    • fstype (filesystem type)
    • path (mount point path)

Example Output:

% ./telegraf --config ~/ws/telegraf.conf --input-filter disk --test
* Plugin: disk, Collection 1
> disk,fstype=hfs,path=/ free=398407520256i,inodes_free=97267461i,inodes_total=121847806i,inodes_used=24580345i,total=499088621568i,used=100418957312i,used_percent=20.131039916242397 1453832006274071563
> disk,fstype=devfs,path=/dev free=0i,inodes_free=0i,inodes_total=628i,inodes_used=628i,total=185856i,used=185856i,used_percent=100 1453832006274137913
> disk,fstype=autofs,path=/net free=0i,inodes_free=0i,inodes_total=0i,inodes_used=0i,total=0i,used=0i,used_percent=0 1453832006274157077
> disk,fstype=autofs,path=/home free=0i,inodes_free=0i,inodes_total=0i,inodes_used=0i,total=0i,used=0i,used_percent=0 1453832006274169688

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

Data collection is based on github.com/shirou/gopsutil. This package handles platform dependencies and converts all timing information to milliseconds.

Measurements & Fields:

  • diskio
    • 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.

Tags:

  • All measurements have the following tags:
    • name (device name)
  • If configured to use serial numbers (default: disabled):
    • serial (device serial number)

Sample Queries:

Calculate percent IO utilization per disk and host:

SELECT 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 derivative(last("weighted_io_time",1ms))/1000 from "diskio" WHERE time > now() - 30m GROUP BY "host","name",time(60s)

Example Output:

% telegraf -config ~/.telegraf/telegraf.conf -input-filter diskio -test
* Plugin: inputs.diskio, Collection 1
> 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