Re: Good default values for disk monitoring

[Paul Theodoropoulos]

It primarily depends upon your workload. What sorts of applications are 
you running on the server? Websites? Database? Email?  Is usage 
generally steady, or bursty?

You'll need to generate some metrics in order to find the best alerting 
point.  For disk IO, I'd recommend using iostat, and leave it running 
for an interval during which you'd feel comfortable that the machine has 
been under what might be peak or high(er) load. e.g.

iostat -hmy 60

will gather statistics for MB/s read/write for the last 60 seconds, 
repeatedly. Watch those values for a while (or go have a coffee and come 
back and examine the scrollback :) - then check what the values are.

To get the 'service time' data, you'd run iostat in 'extended 
statistics' mode:

iostat -hmxy 60

What you might then do is set the monit tests to 1.5x the highest value 
you saw, as a starting point. Obviously you don't want to be alerted all 
the time for otherwise-normal activity, so you can tune it higher/lower 
from there.

On 6/1/2018 22:42 PM, Teresa e Junior wrote:
> Hello! I'm in the process of discovering Monit, and I am happy with 
> the results so far!
>
> I've set up a couple of rules already, but disk I/O is something I 
> find very difficult to understand. Based on the examples I found in 
> the wiki, I have the following rules:
>
> check filesystem root with path /
>   if read  rate > 1 MB/s for 30 cycles then alert
>   if write rate > 1 MB/s for 30 cycles then alert
>   if service time > 10 milliseconds for 3 times within 5 cycles then 
> alert
>
> I would like to know, please, what could be a recommended default 
> value! For instance, I have a personal server in a VMware VPS, with an 
> Intel Xeon E5-2650L v4 CPU, 1 GB RAM, and 20 GB of allocated storage 
> on SSD.
>
> Thank you for your attention!

--
Paul Theodoropoulos
www.anastrophe.com