Re: Disk or I/O latency?

[Martin Pala]

You can use the "check program" to integrate that script to Monit. The script 
should return error in the case that the I/O limit is exceeded: 
https://mmonit.com/monit/documentation/monit.html#PROGRAM-STATUS-TESTING

The next M/Monit release will support custom charts, so it'll be possible to 
render charts for I/O. We also plan to add native I/O monitoring to Monit and 
related charts to M/Monit, so it'll be easier to use.

Best regards,
Martin


> On 26 May 2016, at 14:31, Pierre-Philipp Braun <address@hidden> wrote:
> 
> Many thanks Viktor for your input.  I also need IO performance monitoring 
> (not esp. lacenty like Bryna, graphs reporting usage would yet be nice) so I 
> wrote a little script based on your/Munin's method,
> 
> #!/bin/bash
> 
> [[ ! -d /sys/block/ ]] && echo /sys/block/ does not exist, exiting && exit 1
> #[[ ! -d /var/cache/monit/ ]] && echo /var/cache/monit/ does not exist, 
> exiting && exit 1
> mkdir -p /var/cache/monit/
> 
> for disk in `ls -1 /sys/block/ | egrep -v '^fd|^dm-|^sr'`; do
>         readio=`cat /sys/block/$disk/stat | awk '{print $1}'`
>         writeio=`cat /sys/block/$disk/stat | awk '{print $5}'`
>         echo "$readio,$writeio" >> /var/cache/monit/$disk.stat
>         unset readio writeio
> done
> 
> it produces,
> 
> # pwd
> /var/cache/monit
> # ll
> total 16K
> drwxr-xr-x   2 root root   51 May 26 14:21 .
> drwxr-xr-x. 15 root root 4.0K May 26 14:20 ..
> -rw-r--r--   1 root root   26 May 26 14:21 sda.stat
> -rw-r--r--   1 root root   18 May 26 14:21 sdb.stat
> -rw-r--r--   1 root root   12 May 26 14:21 sdc.stat
> # cat *
> 17579,219210
> 2292,480
> 939,3
> 
> How to integrate this into Monit?  Is CSV a good choice as a format?
> 
> 
> 
> On 18/05/2016 23:05, SZÉPE Viktor wrote:
>> Munin does it by comparing `cat /sys/block/*/stat` e.g `cat
>> /sys/block/sda/stat` with the previous reading. This file contains 11
>> values:
>> https://github.com/munin-monitoring/munin/blob/devel/plugins/node.d.linux/diskstats#L440-L444
>> 
>> 
>> So previous rd_ios minus current rd_ios gives you and average IO/period.
>> You may "remember" these by storing them in a file, for example in
>> /var/cache/monit/sda.stat
>> 
>> 
>> 
>> Idézem/Quoting Graham Smith <address@hidden>:
>> 
>>> I don't think there is anything built in for that. You may not need a
>>> script per se, an application may have an exit status you could use to
>>> denote a fail or success of performance quality. Possibly iostat or
>>> iometer
>>> perhaps.
>>> If it's not a simple numeric output, a wrapper script might not need
>>> to be
>>> long and that could output a simple exit status to denote a success
>>> quality
>>> which monit can handle easier.
>>> 
>>> I always think it's best to keep complexity out of monit and if you
>>> need to
>>> do something fancy a script for anything odd is ultimately more
>>> modular as
>>> you may find other uses for it.
>>> 
>>> Graham
>>> On 18 May 2016 19:04, "Bryan Harris" <address@hidden> wrote:
>>> 
>>>> Hello all,
>>>> 
>>>> Does Monit have a way to measure i/o latency and alert if say a 4k write
>>>> takes longer than some number of ms?  I searched the mailing list and
>>>> manual and do not see anything.  Otherwise I can always monitor a custom
>>>> script for this purpose.
>>>> 
>>>> Thanks in advance.
>>>> 
>>>> V/r,
>>>> Bryan
>>>> 
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>>>> 
>> 
>> 
>> 
>> SZÉPE Viktor
> 
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