Scott Carey wrote:
* Change the linux 'readahead' block device parameter to at least 4MB (8192, see blockdev --setra) -- I don't know if there is a FreeBSD equivalent.
I haven't tested them, but 3ware gives suggestions at
http://www.3ware.com/kb/Article.aspx?id=14852 for tuning their cards
properly under FreeBSD. You cannot get good sequential read performance
from 3ware's cards without doing something about this at the OS level;
the read-ahead on the card itself is minimal and certainly a bottleneck.
As for your comments about drives being faster at the front than the
end, the zcav tool that comes with bonnie++ is a good way to plot that
out, rather than having to split partitions up and do a bunch of manual
testing.
--
Greg Smith 2ndQuadrant US Baltimore, MD
PostgreSQL Training, Services and Support
greg@xxxxxxxxxxxxxxx www.2ndQuadrant.us
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