I'm currently testing a 1 node architecture as I was having problems with afr and multinode performance. write and read performance to glusterfs (single node) is now good, but when running mysql on top of glusterfs, performance drops dramatically due to high cpu usage. mysql is mounted to the glusterfs & glusterfsd is running on the same node. When running a simple query accessing one table, the cpu load from glusterfs / glusterfsd in top are relatively low. When running a 3 table join (18 files must be read, myi,myd,frm for each table, 2 tables per virtual table, so 3*3*2), the glusterfs/glusterfsd cpu load skyrockets stealing the cpu away from mysql processing. So this query on the local fs (ext3) takes 4 seconds, while the single node glusterfs takes 22 seconds. I've adjusted iothreads, iocache, readahead, etc,etc. None of these options make a difference in the cpu load. Tried using posix-locks and then posix. I wonder if glusterfs and mysql are stepping on each other's toes to cause this high load? Might the issue lie in tuning the file system & kernel params? Or is this cpu usage expected load? Thanks.
