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.
> 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:
Then decide whether 10 extents per file is really a problem or not.