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Re: A little RAID experiment

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: A little RAID experiment
From: Stefan Ring <stefanrin@xxxxxxxxx>
Date: Thu, 11 Oct 2012 00:01:37 +0200
Cc: Linux fs XFS <xfs@xxxxxxxxxxx>
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In-reply-to: <20121010212733.GW23644@dastard>
References: <CAAxjCEzh3+doupD=LmgqSbCeYWzn9Ru-vE4T8tOJmoud+28FDQ@xxxxxxxxxxxxxx> <CAAxjCEwYyzTLTJk7SU0t=1SnT-V=7VadtKd0v9qj0soXtJ8XTg@xxxxxxxxxxxxxx> <20121010212733.GW23644@dastard>
> Just inidicates that the working set for your test is much more
> resident in the controller cache - has nothing to do with the disk
> speeds. Tun a larger set of files/workload and the results will end
> up a lot closer to disk speed instead of cache speed...

That's indeed a valid objection, but I just verified that with the
working set size multiplied by the relative cache size difference
(64GB instead of 8GB), the performance stays exactly the same. The new
controller seems to run much better cache control algorithms.

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