Re: Tuning Linux for high-speed disk subsystems

[Marvin Justice <mjustice@boxxtech.com>]

> 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.

-- 
Marvin Justice
Software Developer
BOXX Technologies
www.boxxtech.com
mjustice@boxxtech.com
512-235-6318 (V)
512-835-0434 (F)