Dual-core CPU vs. very large cache

Bill Moran wmoran at collaborativefusion.com
Tue Apr 25 13:07:40 UTC 2006

[First off, the list archives for this list don't seem to be
searchable.  I get the following error:
Unable to read document excerpts '/usr/local/mailman/archives/private/freebsd-performance/htdig/db.excerpts'
Did you run htdig?]

So ... on to the question.

We have some database servers that we're looking to replace with
beefier hardware, mainly because we're expecting our customer base
to grow a lot in the near future.

The current hw is Dell 2850 servers.  These are dual proc (each proc
is hyperthreaded) with Dell PERC controllers driving 4 SCSI-320
disks in a RAID-10.

We're doing our best to simulate high-load in the lab, and the
database consistently bottlenecks on CPU usage.  I'm assuming that
the combination of plenty of RAM and high-speed disks has led to
the CPU being the slowest part of the system.

We're considering two alternatives for the newer hardware:
1) Intel HT CPUs with 8M cache
2) Intel dual-core procs

Our current Dells have 2M cache, and I'm trying to determine whether
the 8M cache will make a significant difference or not.  Can someone
recommend a testing procedure for determining whether adding cache is
worthwhile or not?  I can simulate a test load at any time, but I
don't know how to tell whether the cache is the bottleneck of the
CPU or not.

Bill Moran
Collaborative Fusion Inc.

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