Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Mon Jun 23, 2008 at 09:27:02 +0200, Lars Ellenberg wrote:
>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?
>git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
>
>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>
Indeed it would. I'll have to check and see if it was backported to the
RHEL4 kernel (unless you know off the top of your head).
--
Regards,
Oliver Hookins