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Re: Finding the Bottleneck

This statement makes me wonder:
"Also even the slowest part of a 45G drive will be twice as fast as the
fastest part of a 15G drive."

Are you sure? I never heard this before... might be a 1% difference there,
but twice as fast? The 15G runs at 7200rpms, and I assume the 45G also
does unless its a 10000rpm unit (but I don't think there are any 1000rpm
units for ata interfaces, only scsi, right?) The cache on the 15G is 2Mb,
which I assume is the same on the 45G disk.

"That an average of over 11 messages per second.  Not bad with such tiny

Well, it doesn't seem to come to raw hardware performance here. From "top"
output, the 500mhz CPU isn't loaded and swap is not touched at all
(totally in ram). Many small-mid range servers don't run Raid
configurations. However, it does appear that a Raid setup will help
greatly in this case, even with the lower end hardware specs, don't you

As soon as you clarify the first point, I think we'll be looking far more
closely at Raid solutions (either software or cheap hardware.... which
would be better.... if we go with software the bottleneck might then be
shifted to the CPU?!)


----- Original Message -----
From: "Russell Coker" <russell@coker.com.au>
To: "Jason Lim" <maillist@jasonlim.com>; <debian-isp@lists.debian.org>
Sent: Friday, June 08, 2001 10:43 AM
Subject: Re: Finding the Bottleneck

On Friday 08 June 2001 00:05, Jason Lim wrote:
> 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.

OK.  Software RAID on ATA drives is what you will be using then.

> I'll also scratch the NFS idea since qmail wouldn't work well on it,

Qmail won't work at all on NFS...

> 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
> queue.
> 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?

That an average of over 11 messages per second.  Not bad with such tiny

The first thing to do is to buy some decent hard drives.  Get new IBM
drives of 40G or more capacity and use the first 15M of them (it reduces
seek times and also the first part has a higher transfer rate).  Also
even the slowest part of a 45G drive will be twice as fast as the fastest
part of a 15G drive.

Put the spool and queue on a software RAID-1 over two 45G drives and put
the rest on a software RAID-1 over the two old 15G drives.  Then the
system should be considerably more than twice as fast.

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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