HEADS UP: More CAM fixes.
scottl at samsco.org
Tue Feb 17 12:46:30 PST 2009
Bruce Evans wrote:
> On Tue, 17 Feb 2009, Gary Jennejohn wrote:
>> I tested this with an Adaptec 29160. I saw no real improvement in
>> performance, but also no regressions.
>> I suspect that the old disk I had attached just didn't have enough
>> performance reserves to show an improvement.
>> My test scenario was buildworld. Since /usr/src and /usr/obj were both
>> on the one disk it got a pretty good workout.
> ^^^^ low
>> AMD64 X2 (2.5 GHz) with 4GB of RAM.
> Buildworld hardly uses the disk at all. It reads and writes a few hundred
> MB. Ideally the i/o should go at disk speeds of 50-200MB/S and thus take
> between 20 and 5 seconds. In practice, it will take a few more seconds.
> physically but perhaps even less virtually due to parallelism.
Yes, on modern machines, buildworld is bound almost completely by disk
latency, and not at all by disk or controller bandwidth.
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