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Re: Finding the Bottleneck


Thanks for your detailed reply.

As reliability is not of great importance (only the mail queue will be
there and no critical system files), I'd go for speed and cheap price. The
client doesn't have the huge wads of cash for the optimal system with scsi
drives and 64M cache raid card :-/  So I guess if it comes down to the
crunch, speed and cheap price is it.
I'll also scratch the NFS idea since qmail wouldn't work well on it, and
as you said, there wouldn't be much benefit if the other server has the
same problems as well.

Okay... the server right now is an AMD k6-2 500mhz 128M with 2 15G IBM
drives. At this moment, it is really having trouble processing the mail
sh-2.05# qmail-qstat
messages in queue: 297121
messages in queue but not yet preprocessed: 72333

I checked the log and yesterday it sent about 1 million emails. Do you
think that the above hardware configuration is performing at it's
realistic limit?


----- Original Message -----
From: "Russell Coker" <russell@coker.com.au>
To: "Jason Lim" <maillist@jasonlim.com>; <debian-isp@lists.debian.org>
Cc: <bam@coker.com.au>
Sent: Friday, June 08, 2001 3:42 AM
Subject: Re: Finding the Bottleneck

On Thursday 07 June 2001 20:14, Jason Lim wrote:
> I agree with you... it seems more and more likely that the Disks are
> the limiting factor here.
> I guess the next big thing to do would be to run some form of Raid
> (software or hardware) for the mail queue.
> Does anyone know of a cheap but adequate raid hardware solution? The
> one's I've seen seem to cost quite a bit. I know that the common cheap
> ATA100 Raid cards available now (using the Highpoint HPT370) don't work
> properly on Linux beacuse of the bad driver support. Anyone know of an
> alternative?

For RAID hardware there are three criteria you desire, reliability, low
price, and speed.  You can have at most two of them.

There are a number of cheap hardware RAID solutions out there which would
be quite OK for home use, but not for a server of the type you are
considering.  If you had several redundant servers with the same data
then one of the cheap hardware RAID solutions might do well though.

> Actually... do you think setting up a seperate box (connected via NFS)
> PURELY for mail queue processing would help at all? Or would the
> bottleneck then be shifted to NFS?

If the NFS server has the same disk system then you will only make things
worse.  Anything you could do to give the NFS server better IO
performance could more productively be done to the main server.
Also many of the common Unix mail server programs are specifically
designed to have the queue on a local file system with standard Unix
semantics (Inode numbers etc).  Qmail is one mail server that I have
found to not work with it's queue on NFS, I haven't seriously tried any
others.  I've CC'd Brian May because he does a lot more NFS stuff with
Debian than most people and he may be able to advise you.

I suggest just getting 4 IDE disks and putting everything on a software
RAID-10 apart from /boot (which must be RAID-1 for the boot loader to
work).  It'll get the most bang for the buck!

http://www.coker.com.au/bonnie++/     Bonnie++ hard drive benchmark
http://www.coker.com.au/postal/       Postal SMTP/POP benchmark
http://www.coker.com.au/projects.html Projects I am working on
http://www.coker.com.au/~russell/     My home page

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