Did you delete the output file after running your dd test? I saw significant improvement when I modified my dd test to delete the out file after each run. Ed -----Original Message----- From: gluster-users-bounces at gluster.org [mailto:gluster-users-bounces at gluster.org] On Behalf Of Barry Jaspan Sent: Monday, June 29, 2009 2:49 PM To: gluster-users at gluster.org Subject: AFR, writebehind, and debug/trace I just got started with glusterfs. I read the docs over the weekend and today created a simple setup: two servers exporting a brick and one client mounting them with AFR. I am seeing very poor write performance on a dd test, e.g.: time dd if=/dev/zero of=./local-file bs=8192 count=125000 presumably due to a very large number of write operations (because when I increase the blocksize to 64K, the performance increases by 2x). I enabled the writebehind translator but see no improvement. I then enabled a trace translator on both sides of the writebehind and seem to be seeing that write-behind is not batching any of the operations. Server vol file: volume posix type storage/posix option directory /mnt/glusterfsd-export end-volume volume locks type features/locks subvolumes posix end-volume volume brick type performance/io-threads option thread-count 8 subvolumes locks end-volume volume server type protocol/server option transport-type tcp option auth.addr.brick.allow * subvolumes brick end-volume Client vol file: volume remote1 type protocol/client option transport-type tcp option remote-host web-1 option remote-subvolume brick end-volume volume remote2 type protocol/client option transport-type tcp option remote-host web-2 option remote-subvolume brick end-volume volume replicate type cluster/replicate subvolumes remote1 remote2 end-volume volume trace-below type debug/trace subvolumes replicate end-volume volume writebehind type performance/write-behind option cache-size 1MB subvolumes trace-below end-volume volume trace-above type debug/trace subvolumes writebehind end-volume With this configuration, I re-ran by dd test but with only count=100. The log shows: [root at web-3 glusterfs-mount]# grep trace /var/log/glusterfs/mnt- glusterfs-mount.log | grep above | wc 245 3591 42117 [root at web-3 glusterfs-mount]# grep trace /var/log/glusterfs/mnt- glusterfs-mount.log | grep below | wc 252 3678 43095 So, there are as many writes to trace-below as trace-above. What am I not understanding? Thanks! Barry _______________________________________________ Gluster-users mailing list Gluster-users at gluster.org http://zresearch.com/cgi-bin/mailman/listinfo/gluster-users
