Use of floating point on typical mailserver

[Greg Matthews]

Jeff A. Earickson wrote:
> We have two 8-core T2000s and three 8-core T1000s onsite.  The three T1000s
> handle our webmail front end (horde/imp and associated apache stuff). 
> One T2000 is a web server, and the second T2000 came online a couple of
> weeks ago to handle our IMAP service (dovecot 1.0rc18 currently).  This
> box has an HP MSA50 disk array with fourteen 72GB disks in a mirrored/
> striped ZFS disk pool for homedirs.  All of these systems do a great job,
> and barely break a sweat doing it.
> 
> While I can't speak to the FPU issue directly, I got a bit of advice from
> a Sun engineer on which chipset to buy for what use in Sun-land.  If you
> want floating-point computation speed, buy x86 boxes (Sun V20's, etc) 
> because
> the clock cycle of the x86 chips is so much faster.  If the work is non
> floating-point, then buy Coolthreads servers if the ratio of threads to
> processes is > 4.  How to find out?  Run "prstat" and look at the bottom
> line.  Take the ratio of processes to LWPs.  If the ratio is less than
> four, then buy standard Sparc.  Sparc chips have the advantage that they
> are RISC chips while x86 aren't.  His advice, passed along.

thanks Jeff... the problem is how do I know if my MS/SA/AV/MW boxes use 
a lot of FP?

It seems crazy looking back but our relays used to run on Sun Ultra 5s, 
they were replaced by v60z's (Sun Xeon boxes - not very popular) which 
have done a great job since then but are starting to look a bit long in 
the tooth. Tripling the memory gave them a new lease of life! Whatever 
we replace them with needs to have a reasonable chance of coping for 
another 4 years or so.

most of the grunt work of MS and SA is perl text processing which I 
wouldnt expect to use a lot of FP. I would expect AV engines to be 
similar (searching for signature patterns etc) so my hunch is that there 
is little FP work going on... I'll try asking similar questions 
elsewhere to see if I can figure it out...

Not sure I follow the threads/process argument as it seems to assume 
that you will have the same number of processes running on each box. But 
if I have a "32-way" host, I'll increase the maximum number of MS and 
MTA processes to fill the pipes.

GREG

> 
> Jeff Earickson
> Colby College


-- 
Greg Matthews           01491 692445
Head of UNIX/Linux, iTSS Wallingford

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