On Thu 05 Jun 2003 at 09:09:51, David Smith said:
> current file server. My stress tests thus far have been very positive. 
> It's a 4-CPU (hyperthreaded) Xeon 2Ghz box  with 15,000 RPM SCSI drives.

Hmm, I question the choice of hardware.  Multiprocessing for an NFS box
is either a) pointless or b) detrimental.  Why?  Because NFS isn't
multithreaded.  knfsd will primarily run on one processor, and if the
kernel *does* switch it from one processor to another, you have to re-load
the cache on the other processor with the knfsd code, which is a pretty
big hit.  For NFS, if the choice is between one hefty MP 8-rack-unit
machine and 8 SP 1-rack-unit machines, the latter will be your better
choice.  Segment your file system, which will make Linux happier anyway.
Sure, it's a few more lines in the automount configuration, but that's
less of a headache than one slow NFS server.

Now for multithreaded applications like samba, apache, or slapd, then MP
machines are just fine because they're contiually forking new processes
(or as it were, threads) for each connection.  Thus, on an SP box, the
CPU cache gets re-filled anyway.  So you may as well split the load
between a few different processors.

Something I've come to believe over the last year is that a large
cluster of small, one-use servers is a lot easier to manage than a small
cluster of large, multi-use servers.  There are still some applications
where the reverse is true (like enterprise-size databases or some
supercomputing applications), but your general internet services run
much better when split between a handful of machines.  The other
advantage is that if one goes down, then it's trivial to just nuke it
and copy a complete image over from a working server, rather than
restoring everything from backup and bringing each subsystem back on
line.

-- 
Soren Harward
[EMAIL PROTECTED]

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