Check disk-io
Overview
Checks disk bandwidth over a period of time. The check tracks the maximum bandwidth and alerts if the bandwidth over the last n reads is above a certain percentage (by default 80/90% over the last 5 reads). This works similar to Load5, but at the disk I/O level.
On Linux, the check plugin by default tries to find „important“ disks automatically and returns only useful perfdata information, so as not to waste disk space in a time series database with unnecessary disk information (as in earlier versions). To do this, it looks for disks that are mounted to a folder.
Disk I/O always starts at 10 MiB/sec, but stores the highest measured bandwidth, so it adjusts the RWmax/s value accordingly. For this reason, this check takes some time to warm up its (cached) readings: The check will throw some warnings and criticals during the first major disk activities above 10Mib/sec until the maximum bandwidth of the disk has been determined.
Example: The (shortened) result of ./disk-io --count 5 --warning 80 --critical 90 could look like this:
/dev/dm-4: 0.0B/s read1, 48.7KiB/s write1, 48.7KiB/s total, 227.9MiB/s max
Name ! RWmax/s ! R1/s ! W1/s ! R5/s ! W5/s ! RW5/s
-----+---------+----------+----------+----------+----------+--------------------
dm-0 ! 44.9MiB ! 42.8MiB ! 17.2MiB ! 23.1MiB ! 18.6MiB ! 36.3MiB [CRITICAL]
dm-1 ! 10.0MiB ! 4.7KiB ! 4.0KiB ! 2.0KiB ! 6.8KiB ! 8.7KiB
...
The first line always shows the disk with the currently highest bandwidth (here dm-0).
The table columns mean:
RWmax: Here, a maximum bandwidth of 44.9 MB/sec was determined.
R1, W1: The current bandwidth is 23.6 MB/sec read and 17.2 MB/sec write.
R5, W5: The bandwidth from now to 5 measured values in the past is 23.1 MB/sec read and 18.6 MB/sec write.
First line in the table, RW5: Compared to the current values, there was a higher bandwidth for a while. Since a maximum of 44.9 MB/sec bandwidth has been measured for this disk so far, a mean bandwidth (RW5) value of 36.3 MB/sec results in a warning (
36.3 MB/sec >= 44.9 MB/sec * 80%). The current value of 42.8 MB/sec doesn’t matter, this is only a peak. The check alerts because there is unusual high disk I/O over a certain amount of time.
Hints:
--count=5(the default) while checking every minute means that the check will report an alert if any of your disks have been above a threshold in the last 5 minutes.The check uses the SQLite database
$TEMP/linuxfabrik-monitoring-plugins-disk-io.dbto store its historical data.
Fact Sheet
Check Plugin Download |
https://github.com/Linuxfabrik/monitoring-plugins/tree/main/check-plugins/disk-io |
Check Interval Recommendation |
Once a minute |
Can be called without parameters |
Yes |
Compiled for |
Linux, Windows |
3rd Party Python modules |
|
Handles Periods |
Yes |
Uses SQLite DBs |
|
Help
usage: disk-io [-h] [-V] [--always-ok] [--count COUNT] [--critical CRIT]
[--match MATCH] [--top TOP] [--warning WARN]
Checks disk I/O. If the bandwidth usage of a disk is above the specified
threshold (as a percentage of the maximum bandwidth measured) for a certain
period of time, an alarm is triggered.
options:
-h, --help show this help message and exit
-V, --version show program's version number and exit
--always-ok Always returns OK.
--count COUNT Number of times the value must exceed specified thresholds
before alerting. Default: 5
--critical CRIT Threshold for disk bandwidth saturation (over the last
`--count` measurements) as a percentage of the maximum
bandwidth the disk can support. Default: >= 90
--match MATCH Match on disk names. Uses Python regular expressions
without any external flags like `re.IGNORECASE`. The
regular expression is applied to each line of the output.
Examples: `(?i)example` to match the word "example" in a
case-insensitive manner. `^(?!.*example).*$` to match any
string except "example" (negative lookahead). `(?: ... )*`
is a non-capturing group that matches any sequence of
characters that satisfy the condition inside it, zero or
more times. Default:
--top TOP List x "Top processes that generated the most I/O traffic".
Default: 5
--warning WARN Threshold for disk bandwidth saturation (over the last
`--count` measurements) as a percentage of the maximum
bandwidth the disk can support. Default: >= 80
Usage Examples
Just check disk dm-0 (if listed as /dev/dm-0):
./disk-io --match='.*dm-0$'
Match all disks except vdc, vdh and vdz:
./disk-io --match='^(?:(?!.*vdc|.*vdh|.*vdz).)*$'
Example Output:
/dev/dm-8: 5.6KiB/s read1, 2.2MiB/s write1, 2.2MiB/s total, 10.0MiB/s max
Name ! MntPnts ! DvMppr ! RWmax/s ! R1/s ! W1/s ! R5/s ! W5/s ! RW5/s
-----+----------------+------------------+---------+--------+---------+--------+---------+---------
dm-0 ! / ! rl-root ! 10.0MiB ! 0.0B ! 426.0B ! 0.0B ! 343.0B ! 343.0B
vda2 ! /boot ! ! 10.0MiB ! 0.0B ! 0.0B ! 0.0B ! 0.0B ! 0.0B
vda1 ! /boot/efi ! ! 10.0MiB ! 0.0B ! 0.0B ! 0.0B ! 0.0B ! 0.0B
dm-5 ! /var ! rl-var ! 10.0MiB ! 0.0B ! 586.0B ! 0.0B ! 1.1KiB ! 1.1KiB
dm-8 ! /data ! rl-lv_data ! 10.0MiB ! 5.6KiB ! 2.2MiB ! 8.3KiB ! 2.3MiB ! 2.3MiB
dm-6 ! /tmp ! rl-tmp ! 10.0MiB ! 0.0B ! 4.8KiB ! 0.0B ! 7.1KiB ! 7.1KiB
dm-7 ! /home ! rl-home ! 10.0MiB ! 0.0B ! 0.0B ! 0.0B ! 0.0B ! 0.0B
dm-2 ! /var/tmp ! rl-var_tmp ! 10.0MiB ! 0.0B ! 0.0B ! 0.0B ! 0.0B ! 0.0B
dm-4 ! /var/log ! rl-var_log ! 10.0MiB ! 0.0B ! 51.8KiB ! 0.0B ! 51.2KiB ! 51.2KiB
dm-3 ! /var/log/audit ! rl-var_log_audit ! 10.0MiB ! 0.0B ! 918.0B ! 0.0B ! 876.0B ! 876.0B
Top 5 processes that generate the most I/O traffic (r/w):
1. nfsd: 149.2GiB/5.7TiB
2. systemd: 695.7GiB/169.9GiB
3. systemd-journald: 33.9MiB/124.4GiB
4. icinga2: 7.9GiB/4.9GiB
5. rsyslogd: 114.8MiB/4.1GiB
States
WARN or CRIT if the bandwidth over the last n measured values is above a certain percentage, compared to the all time maximum bandwidth of this drive.
Perfdata / Metrics
Per (matched) disk, where <disk> is the block device name:
Name |
Type |
Description |
|---|---|---|
<disk>_busy_time |
Continous Counter |
Time spent doing actual I/Os (in milliseconds). |
<disk>_read_bytes |
Continous Counter |
Number of bytes read. |
<disk>_read_time |
Continous Counter |
Time spent reading from disk (in milliseconds). |
<disk>_write_bytes |
Continous Counter |
Number of bytes written. |
<disk>_write_time |
Continous Counter |
Time spent writing to disk (in milliseconds). |
Troubleshooting
psutil raised error "not sure how to interpret line '...'"orNothing checked. Running Kernel >= 4.18, this check needs the Python module psutil v5.7.0+Update the
psutillibrary. On RHEL 8+, use at leastpython38andpython38-psutilif usingdnf.
Credits, License
Authors: Linuxfabrik GmbH, Zurich
License: The Unlicense, see LICENSE file.