[DRBD-user] Re: Poor network performance on 0.7.22

Lars Ellenberg lars.ellenberg at linbit.com
Mon Jun 23 09:27:02 CEST 2008

On Mon, Jun 23, 2008 at 02:50:07PM +1000, Oliver Hookins wrote:
> Yet more information on this problem. I've found if I remove one of the
> disks from the software RAID1 on the Secondary in this DRBD resource, the
> transfer speeds jump up to what I would call acceptable levels.
> I've tested each of the disks independently and they are both fine. It seems
> there is some sort of strange interaction going on between DRBD, the md
> layer, and perhaps the Adaptec 2020ZCR card (but I'm not sure). With so many
> layers of I/O abstraction it is hard to know what is going on and what
> particular thing is causing the problem...
> Any bells ringing for anyone?

would this perhaps help a little?

commit e3881a6816b45668df60a426e5c3431ece1539a7
Author: Lars Ellenberg <Lars.Ellenberg at linbit.com>
Date:   Wed Jan 10 23:15:37 2007 -0800

    [PATCH] md: pass down BIO_RW_SYNC in raid{1,10}
    md raidX make_request functions strip off the BIO_RW_SYNC flag, thus
    introducing additional latency.
    Fixing this in raid1 and raid10 seems to be straightforward enough.
    For our particular usage case in DRBD, passing this flag improved some
    initialization time from ~5 minutes to ~5 seconds.
    Acked-by: NeilBrown <neilb at suse.de>
    Signed-off-by: Lars Ellenberg <lars at linbit.com>
    Acked-by: Jens Axboe <jens.axboe at oracle.com>
    Cc: <stable at kernel.org>
    Signed-off-by: Andrew Morton <akpm at osdl.org>
    Signed-off-by: Linus Torvalds <torvalds at osdl.org>

: Lars Ellenberg                           http://www.linbit.com :
: DRBD/HA support and consulting             sales at linbit.com :
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