Purchasing the correct hardware: dual-core intel? Big cache?

Bill Moran wmoran at potentialtech.com
Mon Apr 24 22:20:22 UTC 2006

On Mon, 24 Apr 2006 23:03:59 +0100
"Martin Hepworth" <maxsec at gmail.com> wrote:

> Bill
> depends on the application itself, but more RAM and the disk layout (RAID)
> will be more important than the CPU. Also depends on how write-heavy the
> apps are...

Thanks for the feedback, Martin.

I'm fully aware of the app-dependency - what I'm looking for is a way
to test the application.  I've got 3 different clusters available for
testing, but I'm not sure how to tell if the cache is getting used
heavily or not.

I've already determined that the database server is CPU-bound under
our test load.  With high-speed SCSI disks and battery-backed RAID,
there's not enough IO to stress the disk subsystem.  RAM is almost a
non-issue.  With the machine stressed at full load, it's only using
1/8 of the available RAM.

So, my current bottleneck is CPU power.  And the boss has asked me
for the best way to overcome this bottleneck.  We're looking at either
the same CPUs we already have, but with _huge_ caches (8m) - or going
with more CPUs by getting true dual-core pentiums.

The question this all pivots on is will 8M of cache be a significant
improvement?  If not, then we're going with the dual-core CPUs.  What
I'd like is some way to take an existing system and determine how often
the cache is getting invalidated, so I can make some guesstemate as to
whether more cache will help or not.

> --
> martin
> On 4/24/06, Bill Moran <wmoran at potentialtech.com> wrote:
> >
> >
> > I've been asked to make some hardware recommendations, I'm hoping some
> > folks on the list can make some suggestions.
> >
> > We're looking hard at getting either Intel dual-core procs, or getting
> > hyperthreaded procs with huge (8M) caches.
> >
> > We currently have a few dual proc Intel HT machines that we can test
> > out our workload on, and I'm trying to get a feel for how to determine
> > if a larger cache size will generate better performance than replacing
> > HT procs with full-blown dual-core procs.  We're looking at the 6850
> > from Dell, which supports both processor families:
> >
> > http://www1.us.dell.com/content/products/productdetails.aspx/pedge_6850?c=us&cs=555&l=en&s=biz
> >
> > The goal for these machines is to serve out PosgreSQL databases to as
> > many Apache+php front ends as we can hang off each one.  So we're trying
> > to purchase hardware that will create a DB server that can handle a lot
> > of web server front ends.
> >
> > I have a Dell 2850 (dual HT procs) here that I can use for testing.
> > I'm a little fuzzy on determining how well the cache is working, so I'm
> > stuck on whether or not the 8M cache that's available on the HT units
> > is worth the money or not.  Can anyone suggest a testing methodology
> > that will isolate this particular aspect?
> >
> > --
> > Bill Moran
> > Collaborative Fusion Inc.
> > _______________________________________________
> > freebsd-questions at freebsd.org mailing list
> > http://lists.freebsd.org/mailman/listinfo/freebsd-questions
> > To unsubscribe, send any mail to "
> > freebsd-questions-unsubscribe at freebsd.org"
> >
> _______________________________________________
> freebsd-questions at freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-questions
> To unsubscribe, send any mail to "freebsd-questions-unsubscribe at freebsd.org"
> *
> ************************************************************************************
> This footnote confirms that this email message has been scanned by
> PineApp Mail-SeCure for the presence of malicious code, vandals & computer viruses.
> ************************************************************************************

Bill Moran
Collaborative Fusion Inc.

IMPORTANT: This message contains confidential information and is
intended only for the individual named. If the reader of this
message is not an intended recipient (or the individual
responsible for the delivery of this message to an intended
recipient), please be advised that any re-use, dissemination,
distribution or copying of this message is prohibited. Please
notify the sender immediately by e-mail if you have received
this e-mail by mistake and delete this e-mail from your system.
E-mail transmission cannot be guaranteed to be secure or
error-free as information could be intercepted, corrupted, lost,
destroyed, arrive late or incomplete, or contain viruses. The
sender therefore does not accept liability for any errors or
omissions in the contents of this message, which arise as a
result of e-mail transmission.

More information about the freebsd-questions mailing list