Messages in this thread |  | | Date | Sun, 15 Sep 2002 01:07:53 +0200 | From | Lars Marowsky-Bree <> | Subject | Re: Possible Bug with MD multipath and raid1 on top |
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On 2002-09-14T20:33:07, Oktay Akbal <oktay.akbal@s-tec.de> said:
> I found a very strange effect when using a raid1 on top of multipathing > with Kernel 2.4.18 (Suse-version of it) with a 2-Port qlogic HBA > connecting two arrays.
Is this with or without the patch I recently posted to linux-kernel?
If so, please use the patch at http://lars.marowsky-bree.de/dl/md-mp instead, which is slightly newer and fixes one important (affecting raid0 use) and two minor issues. Please be aware that you are beta-testing code for the time being ;-) (Which is highly appreciated!)
> When I now pull out one of the cables two disks are missing and the > multipath driver correctly uses the second path to the disks and > continues to work. After plugging out the second cable all drives > are marked as failed (mdstat), but the raid1 (md2) is still reported > as functional with one device (md0) missing.
So far this sounds OK. (Even though the updated md-mp patch will _never_ fail the last path but instead return the error to the layer upwards; this protects against certain scenarios in 2.4 where a device error can't be distinguished from a failed path and we don't want that to lead to an inaccessible device)
> All Processes using the raid1-device get stuck and this situation > does not recover. Even some simple process testing the disk-access > got stuck (I think ps showed state L<D).
That's not OK, obviously ;-)
I will try to reproduce this on Monday. As I don't have the hardware, but instead use a loop device (which I can make fail on demand), if I can't reproduce it, it might in fact be the FC driver which gets stuck somehow.
> Even if I'm quite sure that this is a bug, how should I test disk access > without ending in "uninterruptible sleep" ?
Uhm, essentially, you should never get stuck in uninterruptible sleep. All errors should "eventually" time out.
Please compile the kernel with magic-sysrq enabled and check where the processes are stuck using magic-sysrq t. It might help if you piped the results through ksymoops.
Sincerely, Lars Marowsky-Brée <lmb@suse.de>
-- Immortality is an adequate definition of high availability for me. --- Gregory F. Pfister
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