svn commit: r201658 - head/sbin/geom/class/stripe
ivoras at freebsd.org
Wed Jan 6 17:38:34 UTC 2010
2010/1/6 Alexander Motin <mav at freebsd.org>:
> Author: mav
> Date: Wed Jan 6 17:12:18 2010
> New Revision: 201658
> URL: http://svn.freebsd.org/changeset/base/201658
> Increase default block size from 4K to 64K. It was reduces 6 yeard ago,
> when trees were big and FAST mode was enabled by default.
> So small block size doesn't benefits linear I/O operations in FAST and
> significantly slowdowns in ECONOMIC (default) mode. For single stream random
> I/Os so small block doesn't give much benefits, as access time is usually
> bigger then transfer time there. Same time it requires all heads to seek
> together for every single request, reducing performance on parallel load.
I think there was one more reason - though I'm not sure if it is still
valid because of your current and future work - the MAXPHYS
limitation. If MAXPHYS is 128k, with 64k stripes data was only to be
read from maximum of 2 drives. With 4k stripes it would have been read
from 128/4=32 drives, though I agree 4k is too low in any case
nowadays. I usually choose 16k or 32k for my setups.
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