I run a decent amount of 3ware hardware, all under centos-4. There seems
to be some sort of fundamental disagreement between ext3 and 3ware's
hardware RAID5 mode that trashes write performance. As a representative
example, one current setup is 2 9550SX-12 boards in hardware RAID5 mode
(256KB stripe size) with a software RAID0 stripe on top (also 256KB
chunks). bonnie++ results look like this:
mount -t ext3
175 MB/s writes, 352 MB/s reads
mount -t ext3 -o data=writeback
185 MB/s writes, 254 MB/s reads
mount -t ext2
340 MB writes, 266 MB/s reads
XFS on this hardware gets (untuned) about 300 MB/s writes and 400 MB/s
reads. The hardware itself is capable of more, and those results are
representative of several different configs of hardware and software RAID
options.
Any ideas as to what leads to ext3's performance hit? I've tested *lots*
of configurations. It's not the md layer -- 1 card setups see the same
performance hit.
Thanks.
--
Joshua Baker-LePain
Department of Biomedical Engineering
Duke University
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