[DRBD-announce] Re: [DRBD-user] drbd-8.0.14.tar.gz and drbd-8.2.7.tar.gz

[Lars Ellenberg]

On Wed, Nov 12, 2008 at 10:20:08PM +0100, Philipp Reisner wrote:
>  * Support for using barriers to enforce write ordering on the secondary
>    node. New config options: no-disk-barrier, no-disk-drain

let me add here: if your DRBD lives on a battery backed write cache,
and for performance reasons in the past you needed to say "no-disk-flushes",
chances are that you now need this "no-disk-barrier" in addition,
or throughput may degrade again.

do NOT use no-disk-drain if you care for write ordering and there is
anything below drbd in the io stack that may re-order writes.

to put that the other way around: only use no-disk-drain if you
use the no-op io scheduler, AND all the lower level transports involved
do not reorder anything before a write is completed as "on stable storage".

-- 
: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
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