[libvirt-users] Performance tuning questions for mail server

[Emmanuel Noobadmin]

On 10/6/11, Alex <mysqlstudent at gmail.com> wrote:
> This mail server does manage a lot of mail per day, but not enough to
> even consume the 8GB I've allocated, and the "mailq" command typically
> takes a few seconds to respond, even when there's only a few messages
> in the queue.
>
> iotop may report as much as 2M/s on the host, with an average of about
> 400-600K/s. Does that seem like a lot? I can write like 80MB/s at
> least using dd to test.

I had similar problems previously. The crux in my case is the number
of IOPS possible. 100K of 2KB file writes is still 2MB/s but requires
a lot more IO overheads than 1 single 2MB file.

Recommendations that I was given which stopped the system from locking
up included
1. use ionice on the mail process
2. change the IO scheduler/elevator from the default CFQ
3. switch from file-based virtual drives to raw disk devices
4. mount filesystems with noatime

Also, are you using RAID 5?