On Tue, Feb 28, 2012 at 09:14:41AM +0000, Brian Candler wrote: > On Tue, Feb 28, 2012 at 12:48:13PM +1100, Dave Chinner wrote: > > > Write cache: enabled > > > > There's your problem. You should read all the relevant sections on > > write caches in the XFS FAQ. e.g: > > > > http://xfs.org/index.php/XFS_FAQ#Q._Which_settings_does_my_RAID_controller_need_.3F > > As a side question to this: if I am using Linux's md software RAID with an > HBA, and XFS is using write barriers (as I believe it does by default), is > it still necessary to disable write caching on the drives? No. The MD layers pass the correct flushes to the drives now. > My reading of the FAQ suggests that the write barrier by itself should be > sufficient - but this requires that the md RAID driver implements write > barriers correctly. I seem to remember reading a long time ago that LVM > and/or dmraid didn't, although that may be different now. It has since about 2.6.35. > Incidentally I'm using 'mdadm ... -b internal' to ensure that the RAID array > marks dirty areas, so that if a write part-completes (e.g. a block is > written to only one half of a RAID1) then at next power-up this should be > made consistent again. Assuming that the dirty area tracking uses write cache flushes correctly. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
