I'm currently experimenting with the ccd driver to speed up a particular
file system. I'm using an NCR wide SCSI controller and four IBM DCHS09X
disk drives. The drives are able to transfer 7-9 MB/second when using
large block reads from the raw device. When I measure the performance for
all four drives at once, I still get a aggregated transfer rate of
around 28 MB per second.
When I set up a ccd device with the four disks, I am unable to read more
than 14-15 MB per second from the stripe set. I tried various different
interleave factors (and found that 36 seems to be the optimum value).
Does anyone have an explanation for this limitation?
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