> Date: Tue, 13 Jul 2010 10:40:06 -0400 > From: Richard Andrews <[email protected]> > Subject: Optimizing disk i/o performance > To: "'[email protected]'" <[email protected]> > Message-ID: > <496a9f867c284a47a25bf0fb1a1ef81930dc7d0...@exchange-mb- > 01.office.pelmorex.com> > > Content-Type: text/plain; charset="us-ascii" > > Hello, > > I'm investigating the most ideal settings to improve the performance of > a glusterfs implementation. Are there optimal settings for the > following parameters with respect to the Perc 6/I rev.122 controllers? > > /sys/block/sda/queue/nr_requests > Blockdev Readahead value (blockdev -getra /dev/sda) > > Currently the default values for CentOS are 128 and 256 respectively. > I understand that increasing nr_requests will have a memory usage > impact and changing the readahead parameters may have a memory usage > impact. > > Regards, > > Richard Andrews > Pelmorex Media Inc.
we typically setup a blockdev --setra of about 4k or 8k blocks per physical device. memory is cheap. It usually makes a better-than-50% improvement in IO of large files. Here is an example. sdb is a 6-way raid set, so it gets 1k per disk. This is a SLES10 system. RH/CentOS may vary in where or how you do this. # cat /etc/init.d/boot.local #! /bin/sh blockdev --setra 4096 /dev/sdc blockdev --setra 4096 /dev/sde blockdev --setra 4096 /dev/sdf blockdev --setra 4096 /dev/sdg blockdev --setra 4096 /dev/sdh blockdev --setra 4096 /dev/sdi blockdev --setra 6144 /dev/sdb echo noop > /sys/block/sdc/queue/scheduler echo noop > /sys/block/sde/queue/scheduler echo noop > /sys/block/sdf/queue/scheduler echo noop > /sys/block/sdg/queue/scheduler echo noop > /sys/block/sdh/queue/scheduler echo noop > /sys/block/sdi/queue/scheduler Resetting the scheduler means that Linux and the RAID controller are not competing for who has the best IO scheduler. Since you cannot turn off RAID controller scheduling (except by avoiding RAID) we keep Linux out of the picture. --John _______________________________________________ Linux-PowerEdge mailing list [email protected] https://lists.us.dell.com/mailman/listinfo/linux-poweredge Please read the FAQ at http://lists.us.dell.com/faq
