On Tue, 2011-12-13 at 13:23 -0600, Stan Hoeppner wrote: > > hoping for help, I'm experiencing a strange performance issue on debian > > squeeze. The host is running 2.6.32-5-amd64 on a Xen enterprise cluster, > > filesystem lies on a NetApp storage mounted using ISCSI. Other virtual > > hosts on that cluster does not have the same performance problems.
I have to correct that statement. All hosts have performance problems. > > As soon as I start to copy i.e. a 2GB file local or to a remote host, > > the iowait is rising and the host feels jerking. > > > > sar reports %iowait > 60 > > > > Activating block_dump for a minute (echo 1 > /proc/sys/vm/block_dump) > > shows me that the process causing the iowait is jbd2 which is part of > > the ext4 filesystem. > > Any ideas howto tweak the fs for better performance? > > Ext4 isn't the source of the problem but simply the messenger in this > case. Try the deadline and noop elevators and see if that helps. The No it doesn't, same bad performance regardless of which elevator is used. > default CFQ elevator is known to suck. Also, post the block layer > device driver you're using to access the virtual disk. xen-blkfront is loaded. Regdards Frank -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/1324282142.8928.73.ca...@nero.internal.friendscout24.de