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Re: priocscan vs fcfs

On Wed, 2 Dec 2015, Michael van Elst wrote:

fcfs is also the "neutral" queue for drivers stacking on top of
each other. The queue sorting should really only be done
at one level.

But raidframe is more complicated because it does its own queuing
and sorting outside of this schema, in particular when it has to
read-modify-write stripe sets for small I/O.

That's probably why setting the queues all to fcfs is the best
for you.

Thanks a lot for this clear analysis Michael.

I can now confirm the results I've witnessed earlier, I've ran a couple of
benchmarks, including bonnie++ and iozone, the latter shows a ratio of x5 in
favor of the fsfc strategy for every type of operation. For those interested,
iozone spreadsheet output is available here (OOo / LibreOffice):

For each subset, first column is the amount of data written (from 64K to 4M)
and first row is the block size.

Emile `iMil' Heitor * <imil@{,,}>
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