Re: Tuning Linux for high-speed disk subsystems
Andreas Dilger (email@example.com)
Thu, 22 Nov 2001 09:30:32 -0700
> Re: Tuning Linux for high-speed disk subsystems
> > As I count your disks may be the double for the best case. I read here on
> > LKML a post that someone claims that W2k deliever 250 MB/s with such a
> > configuration. Linux 2.4 should do the same. Ask the SCSI gurus.
> That may have been my post you refer to. With 2x5 disks, each capable of
> 50 MB/s by itself, we can stream 255 MB/s very smoothly in either direction
> with W2K --- as long as FILE_FLAG_NOBUFFER is used. With standard
> reads the number is more like 100 MB/s if I recall correctly, so the buffer
> cache can definitely get in the way.
> With Linux + XFS I was getting 250 MB/s read and 220 MB/s write (with a
> bit less smoothness than W2K) using O_DIRECT and no high mem to avoid
> bounce buffer copies. Using standard reads the numbers drop to around
> 120 MB/s. That was a couple of weeks ago and I want to try tweaking some
> more but a co-worker has "borrowed" pieces of the hardware for the moment.
Jusy FYI, Linus announced that he had returned Andrea's O_DIRECT support
to the most recent 2.4.15-pre kernel, so you are no longer restricted to
using XFS for no-cache I/O. Whether you will be able to beat XFS for
speed using any other filesystem is another question.
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