Vladimir Barac wrote:
Oracle 10.2.0.2, OCFS2, single instance database, NetApp FCP disks filesystemio_options=setall db_file_multiblock_read_count=128Do we need to set readahead to greater than 0 for OCFS2? What would be ideal value? How to measure impact – positive/negative?Storage admins would prefered "blockdev –-setra" to be set to maximum value, to speed up filesystem backups. On the other hand, since oracle will use O_DIRECT on OCFS2, I believe we don't need readahead to be set.
It's (as always) a little application dependent, although my experience has been that very few databases benefit from read-ahead. (Just some warehouses/datamarts.) NetApp has published best practices and they have a decent paragraph about this - as of May 2008 they generally recommend not using readahead.
Furthermore, you certainly shouldn't tune your storage system to perform fast backups and do everything else a little more slowly. :) And if someday you move toward incremental or even updated image copy backups, then the readahead won't benefit at all for backups.
-Jeremy -- Jeremy Schneider Chicago, IL http://www.ardentperf.com -- http://www.freelists.org/webpage/oracle-l