Robert G. Brown
rgb at phy.duke.edu
Thu Feb 28 16:07:25 EST 2002
I'd like to request comments on a couple of dual Athlon motherboards.
We are considering both the Tyan Tiger 2466N (760 MPX) and the MSI K7D
Master (MS-6501) (also 760 MPX). Our local vendor "supports" MSI
motherboards (which just means that we deal with them rather than Tyan
in the event of a return, but which makes it reasonable to use the MSI
all things being equal). We are going with 760 MPX to get the 64/66 PCI
slots, of course -- we actually have a small stack of 2460 Tigers which
are not totally painless but which we've more or less tamed.
Any experiences yet, good or bad, with either motherboard? The vendor
is probably going to loan us an MSI-based dual to test, but there's
nothing like the experience of somebody actually running a cluster if
there is anybody out there already doing so.
I'd also like comments on RAID alternatives. We have a group who needs
about 500 GB of RAID. We just got a Promise UltraTrak100 TX8 (IDE-SCSI)
RAID chassis that advertised decent itself as OS-independent plug and
play -- attach to SCSI bus and go. The first unit we were shipped
didn't work under any OS. The second we were shipped we got the vendor
(Megahaus) to verify function before shipping and it does "work", but it
returns unbelieveably poor performance at RAID 5 -- a (very) few MB/sec
-- under bonnie. From this we learned (among many things:-) that
vendors often quote performance numbers on a RAID from its RAID 0
configuration, which would kind of funny if it weren't for the murderous
impulses it creates when you learn that their numbers are some sort of
cruel joke under RAID 5.
We are twisting Megahaus's arm to take it back and give us our money
back (they are complaining that it is more than thirty days since they
delivered the FIRST unit, but we've only had a working unit for about
two weeks and do not want it if its SCSI performance is that abysmal).
We are then stuck looking for an alternative at roughly the same cost.
Our alternatives seem to be:
a) Another IDE-RAID enclosure, perhaps from a better manufacturer.
However, at this point we're more than a bit concerned about the gap
between vendor performance claims and reality. There are vendors that
assert 100 MB/sec read times, but we are concerned that they mean "at
RAID 0" which is useless to us. We need real-world loaded numbers at
RAID 5 (e.g. multiple instances of bonnie). Folks we know locally who
have e.g. zero-d chassis report real world throughput more like 20
MB/sec RW, but their boxes are a year or two old and may not reflect
current rates. 20 MB/sec is pretty much the LOWEST rate we could
tolerate in this application under multithreaded load, and we'd like
something better. Any enclosure/controllers out there that give good-to
excellent performance that you'd care to recommend?
b) md-raid, either ide or scsi, on a straight linux server. We know
that this works remarkably well. We run md raid in the departmental
server (scsi, with a stack of 36 GB disks in RAID 5) and get excellent
performance -- ~40 MB/sec write throughput and even better for read.
Unfortunately large SCSI disks are still excessively expensive and we
don't have the budget to reach 500 GB with SCSI disks for this cluster.
IDE is cheap and easy, but we would like a bit of assurance that linux
won't have (e.g. DMA) problems when dealing with 6-8 ide controllers on
one bus. Is anyone doing this? Good, bad experiences, hardware
recommendations or gotchas all welcome.
c) SCSI RAID. Definitely works, definitely high performance, but also
the most expensive and again, we won't be able to afford to reach our
design spec with the money allocated to this ($5-6K total).
If we have to fall back to SCSI we will and will live with a smaller
RAID than we had hoped, but we'd very much like to first find out if
IDE-based RAID solutions (RAID 5 on ~500GB total disk) with >20 MB sec
worst case write rates under heavy load exist.
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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