On 4/11/12 9:55 PM, David Fuller wrote: > Dave, > > Thanks so much for that informative read. This helps me fight my case that systematic > defrags are not needed and are bad for the system in general. > > After reading this I did do some checks against some of our larger tables and found that > on average we are storing about 2.5GB per extent. For me that seems pretty reasonable > to me and does not require defrag'ing at this time. I've also added a visual aid to that faq entry to show how quickly the frag factor approaches 100% :) -Eric > --David Fuller > > > <http://www.topshelfads.com/email/sig/epochbestbilling.jpg> > > > On Wed, Apr 11, 2012 at 7:16 PM, Dave Chinner <david@xxxxxxxxxxxxx <mailto:david@xxxxxxxxxxxxx>> wrote: > > On Wed, Apr 11, 2012 at 06:04:25PM -0700, David Fuller wrote: > > We seen to be having an issue whereby our database server > > gets to 90% or higher fragmentation. When it gets to this point > > we would need to remove form production and defrag using the > > xfs_fsr tool. > > Bad assumption. > > > The server does get a lot of writes and reads. Is > > there something we can do to reduce the fragmentation or could > > this be a result of hard disk tweaks we use or mount options? > > > > here is some fo the tweaks we do: > > > > /bin/echo "512" > /sys/block/sda/queue/read_ahead_kb > > /bin/echo "10000" > /sys/block/sda/queue/nr_requests > > /bin/echo "512" > /sys/block/sdb/queue/read_ahead_kb > > /bin/echo "10000" > /sys/block/sdb/queue/nr_requests > > /bin/echo "noop" > /sys/block/sda/queue/scheduler > > /bin/echo "noop" > /sys/block/sdb/queue/scheduler > > They have no effect on filesystem fragmentation. > > > Adn here are the mount options on one of our servers: > > > > xfs rw,noikeep,allocsize=256M,logbufs=8,sunit=128,swidth=2304 > > > > the sunit and swidth vary on each server based on disk drives. > > > > We do use LVM on the volume where the mysql data is stored > > as we need this for snapshotting. Here is an example of a current state: > > > > xfs_db -c frag -r /dev/mapper/vgmysql-lvmysql > > actual 42586, ideal 3134, fragmentation factor 92.64% > > Read this first: > > http://xfs.org/index.php/XFS_FAQ#Q:_The_xfs_db_.22frag.22_command_says_I.27m_over_50.25.__Is_that_bad.3F > > Then decide whether 10 extents per file is really a problem or not. > > Cheers, > > Dave. > -- > Dave Chinner > david@xxxxxxxxxxxxx <mailto:david@xxxxxxxxxxxxx> > > > > > _______________________________________________ > xfs mailing list > xfs@xxxxxxxxxxx > http://oss.sgi.com/mailman/listinfo/xfs _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
