On Sat, Jul 4, 2009 at 1:38 AM, James Lever<j...@jamver.id.au> wrote: > > On 04/07/2009, at 1:49 PM, Ross Walker wrote: > >> I ran some benchmarks back when verifying this, but didn't keep them >> unfortunately. >> >> You can google: XFS Barrier LVM OR EVMS and see the threads about this. > > Interesting reading. Testing seems to show that either it's not relevant or > there is something interesting going on with ext3 as a separate case.
Barriers are by default are disabled on ext3 mounts... Google it and you'll see interesting threads in the LKML. Seems there was some serious performance degradation in using them. A lot of decisions in Linux are made in favor of performance over data consistency. >> When you do send me a copy, try both on a straight partition then on a >> LVM volume and always use NFS sync, but when exporting use the >> no_wdelay option if you don't already that eliminates slow downs with >> NFS sync on Linux. > > > The numbers below seem to indicate that either there is no barrier issues > here, or the BBWC in the raid controller makes them more-or-less invisible > as the ext3fs volume below is directly onto the exposed LUN while the xfs > partition is on top of LVM2. > > It does, however, show that xfs is much faster for deletes. Actually it's LVM/EVMS that hides the barrier performance problems because they act as a barrier filter (because they don't support barriers), so running on LVM/EVMS shows great performance, but also the #1 reason that people complain XFS isn't reliable during a system failure, which is all because logging isn't done properly without barriers! -Ross _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
