On Dec 1, 2008, at 11:45 PM, Jan Mikkelsen wrote:
Replying to my own post ...
I have done a test on the same machine comparing 6.3-p1 to 7.1-
PRE. The performance is the expected ~6MB/s (because of the lack
of cache) on 6.3-p1, so the BIOS change doesn't seem to be at fault.
This seems to be a regression somewhere between 6.3 to 7.1. The
Areca driver is the same in 6.3 and 7.1, so the problem seems to be
elsewhere.
I think this is more than just a "performance" problem. The
observations with gstat showing extremely high ms/w values (I have
seen them as high as 22000) makes it look like IO completion
interrupts are being lost.
Any suggestions on where to look next? Are there obvious candidates?
ATA maximum block transfer has dropped from 128k to 64k in 7.x. Am
not sure where the handle is to tweak it back up but has slowed peak
thruput on my Dell PE400SC. Can watch with "systat -v"
Worse, I have a stripped array of 2 drives that won't transfer more
than 43k at a chunk because apparently the stripe metadata didn't
align nicely on 64k multiples.
--
David Kelly N4HHE, [EMAIL PROTECTED]
========================================================================
Whom computers would destroy, they must first drive mad.
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