[Beowulf] Re: SATA or SCSI drives - Multiple Read/write speeds.

Robert G. Brown rgb at phy.duke.edu
Wed Dec 10 14:07:53 EST 2003

On Wed, 10 Dec 2003, Robin Laing wrote:

> > I have to ask.  Is it a P4?  Strictly empirically I have experienced
> > similar things even without filling memory.  I actually moved my
> > fileserver off onto a Celeron (which it has run flawlessly) because it
> > was so visible, so annoying.
> Dell P4 with 512M ram.  IDE drive.

One thing Mark suggested (offline, I think) is that TOO MUCH memory can
confuse the caching system of at least some kernels.  Since I never
fully debugged this problem, but instead worked around it (a Celeron,
memory, motherboard, case costs maybe $350 and my time and annoyance are
worth much more than this) I don't know if this is true or not, but it
got to where it could actually crash the system when it was running as
an NFS server with lots of sporadic traffic.  It behaved like it was
swapping (and getting behind in swapping at that), but it wasn't.  It
may well have been a memory management problem, but it seemed pretty
specific to that system.

> > worked.  AMD or Celeron or PIII are all just fine.
> Even more reason for me to stick with AMD's.

Ya, me too.  Although the P4 has worked fine since I stopped making it a
server.  I still get rare mini-delays -- it seems a bit more sluggish
than a 1.8 MHz system with really fast memory has ANY business being --
but overall it is satisfactory.

> I find that my P90 at home with UWSCSI is faster most of the time than 
> my computer at work.
> This thread has sure opened up some debate.  I didn't think it would 
> raise the number of issues it has.

Yeah, it's what I love about this list.  Ask the right question, and the
list generates what amounts to a textbook on the technology, tools, and
current best practice.  Poor Jeffrey then has to pick from all this and
condense it for CM.  By tonight, Jeffrey! ;-)

Oh wait, that's my deadline too...:-(

Grumble.  Off to the salt mines.  Except that I'm double parked, with
the final exam for the course I'm teaching being given in a few hours.
So Doug may have to wait a few days for this one...


Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu

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