Re: [exim] Spamassassin + Exim4 high IO Wait

On Tue, Sep 19, 2006 at 01:18:59PM +0100, Mark Adams wrote:
> I was hoping to draw from the pool of experience that the exim mailing
> list has, as I realise this is a spamassassin or other issue. We are
> running exim4.62-4 with Spamassassin 3.1.4-4 and suffering extremely
> high IO Wait times on the server whenever spamassassin scans an incoming
> email. Exim4 is setup as defaults (spamd running locally on standard
> port) so no configuration was changed. Spamassassin has not had any
> rules added to it. The server goes from 1-2% wait times spiking to
> between 20-90% when spamd is scanning an email, this lasts for a few
> seconds and then drops back down to normal. This is a system with raided
> SATA drives on a LVG that also serves small SMB shares. It serves around
> 40 mail users.
>
> I have not had this problem on servers with SCSI drives, or on servers
> that use SATA but are strictly mail servers.
>
> Has anyone had this issue? any ideas appreciated.

Do you have auto-learn and SA's bayesian mode enabled? If
so you may be seeing a lot of write activity from SA
updating its dictionaries (especially if you're using the
default GDBM back-end, which is very inefficient).

To assist in diagnosing, you might want to install iostat
or similar and see what pattern of activity (number of
transactions, number of blocks read/written) you're seeing
during mail scanning.

--
``It's a small world, but I wouldn't want to have to paint it.''
(Chic Murray)