high iowait

Paul Graydon paul at paulgraydon.co.uk
Wed Jun 30 06:21:01 UTC 2010

Install iotop on the box and give it a shot.  It's like top but for I/O 
processes, and should tell you what process is doing a lot of reading 
and writing, so hopefully you can track down the problem.
Also might be worth keeping an eye on your swap usage and general memory 
health ("free -m", then look at the figure on the second row under 
'free') , if you've not got much free then the system will be spending 
time paging stuff to disk.

If you've not got anything monitoring standard server metrics (something 
I always recommend), I'd suggest installing munin and munin-node.  It's 
great as a single or for monitoring a small number of servers, but 
doesn't scale that well and isn't as flexible as some of the main 
monitoring software.  It is extremely easy to get set up and running.

Kaushal Shriyan wrote:
> Hi
> Is there a way to know what causes high iowait on ubuntu server. I see
> high %wa intermittently on hardy 8.04 server. I have tomcat server
> running on it.
> Can it be alerted via email if for specific reason it occurs.
> Please suggest/guide further.
> Thanks
> Kaushal

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