Very Computer

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
--

fixing everybody's troubles, everybody's but mine, + Learning & Res. Services
someone must have told them that I was doing fine. + Oulu University, Finland

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