Disk 100% busy

[Will Saxon]

-----Original Message-----
From:	Ronald Klop [mailto:ronald-freebsd8 at klop.yi.org]
Sent:	Sun 2005-10-16 12:40
To:	Will Saxon; stable at freebsd.org
Cc:	
Subject:	Re: Disk 100% busy

> On Sun, 16 Oct 2005 15:16:34 +0200, Will Saxon <WillS at housing.ufl.edu>  
> wrote:
> 
> > I am trying to diagnose a problem whereby a virus scanner (clam
> > antivirus) is taking too long to scan attachments on a mail server. We
> > have an attachment limitation of 20MB and an attachment of 7-20MB can
> > take over 3 minutes to scan. This often causes the sending mail server
> > to timeout and resend the mail.
> >
> > In this case, my mail gateway is is a dual 3.06GHz Xeon with 1GB of ram
> > and 2 36GB 15krpm drives in a raid-1 on a smart array 6i (cciss)
> > controller. I am running FreeBSD 5.4-RELEASE-p1.
> >
> > Systat -vmstat reports the disk mirror is 100% busy at all times on this
> > machine, with an average of around 300 tps at 15KB/t. This seems wrong
> > to me, as these numbers are maintained even when the system doesn't
> > otherwise appear busy. We don't seem to be swamped by log writes. How
> > can I tell what's generating these disk writes? At the moment the 100%
> > disk utilization is the only thing I can see that would cause the
> > scanning delay. The machine overall is sluggish with file operations.

> How many e-mails do you process every second/minute?
> Do you use softupdates are is the filesystem mounted 'sync'.
> Change the mailserver to first accept the message, then scan it, then  
> deliver it. In that case you have much more control over how many messages  
> are scanned at the same time, etc..

I completely forgot that I had the partition mounted 'sync'. That might explain things a bit, huh. 

I am using qmail - the author indicates that softupdates is not recommended. However, I am going to give it a shot and see if I start losing mail as he suggests may happen.

Thanks for answering!

-Will