gstripe performance oddity
sobomax at FreeBSD.org
Fri Jan 2 06:21:49 UTC 2009
Joel Jacobson wrote:
> i tried sending this to freebsd-geom but got no response, so i'll try a
> higher traffic superset list...
> i have a bit of a weird issue, which i suspect is a configuration
> problem, and was looking for a little advice. i have an LSI JBOD box
> with a bunch of SAS drives that i would like to gstripe together. each
> drive individually seems to be able to do about 80 MB/sec streaming
> write, and doing parallel dd's gives me the 160 MB/sec i would expect.
> if i gstripe them together with a 256k stripe width, i only see 80
> MB/sec, though.
> if, however, i newfs/mount it as ufs and then dd myself a big file, that
> gets me about 120-130 MB/sec.
> why does mounting matter?
You will see dd write speed increase on stripe only if you are using
block size (bs=XX) larger than stripe size, so that you should try dd
bs=512k or something and see if it helps.
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