Disk 100% busy

[Ronald Klop]

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..

Ronald.


-- 
  Ronald Klop
  Amsterdam, The Netherlands