SCSI, two BT-958 or one BT-952?

SCSI, two BT-958 or one BT-952?

Post by Trent Piep » Fri, 26 Jun 1998 04:00:00

I'm planning a machine that will serve as a NFS server for an 8 machine
beowulf cluster.  To start with I was planning on getting 4 ultrastar 9ZX
drives spread across two scsi channels.  It looks like I can either get two
BT-958 cards, or a dual channel BT-952 card.  The 958s would cost about $310
total, vs $180 for the 952, but in light of the whole cost of the server, it's
no big deal.  The 952 would save a PCI slot, which would be very nice, since I
might otherwise need to get one ISA ethernet card (plus 2 PCI net cards).

So the 952 seems obvious, but it's a flashpoint card.  How is linux flashpoint
support?  I've been using multimaster cards for years, and they work great.
Will the greater CPU overhead of the flashpoint make a difference for an NFS
server?  This will be a dual CPU system, how well tested is flashpoint with
SMP?  I know some device drivers get unstable under SMP.
|Gazing up to the breeze of the heavens \ on a quest, meaning, reason  |
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1. Mylex (Buslogic) BT-950 vs. BT-958

We currently have two BT-950 (Flashpoint) UW SCSI adapters in a dual
PII 450 MHz machine. One adapter has three Seagate Cheetahs, the other
two. One disk is root, the remaining 4 comprise one raid0 partition. I have
been benchmarking, and while speed is excellent, I am worried about
the cpu consumption. Bonnie says

              -------Sequential Output-------- ---Sequential Input-- --Random--
              -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU  /sec %CPU
         2000  8629 98.0 58084 80.2 22013 70.8  9037 96.7 52675 89.3 405.4  7.2

Even block writes use 80% of cpu. I also used time(1) on this Bonnie
process, and it reported that 40% of the cpu comsumption was system,
60% user.

Iozone reported similar speeds but system cpu consumption was 95%,
user cpu 5%. Is there any way to determine, what that system cpu usage
is? Is it mainly Linux raid implementation's overhead or is it the
Mylex drivers?

I tried also with raid5, and cpu consumption was about the same, plus
the md_thread process taking around 13% of cpu.

Finally, it would be nice to know if upgrading to BT-958 is worth the
price differential.

Janne Himanka

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