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:

quoted

quoted

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@fromorbit.com

_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs