Mark Hahn wrote:
15 drives and 64K chunks gives 960K per stripe.
The raid0 code should set the read-ahead to twice that: 1920K
which I would have thought would be enough, but apparently not.
choosing the RA size should depend in some way on speed, shouldn't it?
after all, the goal is to have enough reads queued to avoid a "stall"
while un-read-ahead-ed sectors pass under the head. for a typical
60 MB/s, 7200 rpm disk, a track is .5 MB. the heuristic above only reads
ahead .12 MB...
While I'm sure you realize it, some reader won't, so I'll point out that
a cylinder is all the tracks which can be read without a seek, and
cylinder size is track size times number of data heads. If you want max
speed you can read that much off a drive at a time...
--
bill davidsen <[EMAIL PROTECTED]>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979
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