readv: parallel or sequential?
ivoras at freebsd.org
Fri Dec 7 06:11:53 PST 2007
Bernd Walter wrote:
> I wonder if the kernel can read a single file in parallel, because
> disk heads can't be on multiple positions at the same time.
They can be in case of RAID0 and similar schemes.
> ZFS does fill read cache in parallel if it knowns that there are enough
> spindels, but in every other case the FS doesn't know about multiple
> In case of ZFS you don't have to care much about it in you application
> because the next sequentiel fileread will use the previously parallel
> prefilled cache.
Yes, ZFS is supposed to be doing marvelous things with IO prediction and
scheduling, but I think even basic "ladder" scheduling done in FreeBSD
could in theory help in tight spots with multiple requests.
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