readv: parallel or sequential?

[Ivan Voras]

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
> spindels.
> 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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