BUG (Deadlock) in 2.6.10

BUG (Deadlock) in 2.6.10

[Christian Schmid]

Hello.

Just for your information: There is a deadlock in the following situation:

MD2 is Raid 0 with 3 disks. sda1 sdb1 sdc1
MD3 is Raid 0 with 3 disks. sdd1 sde1 sdf1
MD4 is Raid 1 with 2 disks. MD2 and MD3!!

If a disk in MD2 fails, MD2 completely fails. MD4 SHOULD now mark disk 1 (MD2) as faulty but does 
not. Instead there is a dead-lock. "sync" hangs as well. Had to reboot.

I am now using the native Raid 10. Is this stable enough?

Best regards,
Chris - RapidTec

RE: BUG (Deadlock) in 2.6.10

[Guy]

I don't know about the dead lock, or the native RAID10,  but you setup is
not the best.

It would be much better to have this config:
MD2 is RAID1 with 2 disks sda1 sdd1
MD3 is RAID1 with 2 disks sdb1 sde1
MD4 is RAID1 with 2 disks sdc1 sdf1
MD5 is RAID0 with 3 disks MD2 MD3 MD4

Now when a disk fails MD5 will not "see" the failure, if fact, each of the
RAID1 arrays can lose 1 disk and not cause MD5 to fail.  A re-sync of 1 disk
will only affect 1 array.

With the setup you had, assume no dead lock...  If you lose 1 disk, 3 disks
go off-line.  When you replace the 1 disk, you must re-sync 3 disks.

Guy

-----Original Message-----
From: linux-raid-owner@vger.kernel.org
[mailto:linux-raid-owner@vger.kernel.org] On Behalf Of Christian Schmid
Sent: Sunday, February 27, 2005 10:34 AM
To: mingo@redhat.com; neilb@cse.unsw.edu.au; linux-raid@vger.kernel.org
Subject: BUG (Deadlock) in 2.6.10

Hello.

Just for your information: There is a deadlock in the following situation:

MD2 is Raid 0 with 3 disks. sda1 sdb1 sdc1
MD3 is Raid 0 with 3 disks. sdd1 sde1 sdf1
MD4 is Raid 1 with 2 disks. MD2 and MD3!!

If a disk in MD2 fails, MD2 completely fails. MD4 SHOULD now mark disk 1
(MD2) as faulty but does 
not. Instead there is a dead-lock. "sync" hangs as well. Had to reboot.

I am now using the native Raid 10. Is this stable enough?

Best regards,
Chris - RapidTec
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Re: BUG (Deadlock) in 2.6.10

[Neil Brown]

On Sunday February 27, webmaster@rapidforum.com wrote:
> Hello.
> 
> Just for your information: There is a deadlock in the following situation:
> 
> MD2 is Raid 0 with 3 disks. sda1 sdb1 sdc1
> MD3 is Raid 0 with 3 disks. sdd1 sde1 sdf1
> MD4 is Raid 1 with 2 disks. MD2 and MD3!!
> 
> If a disk in MD2 fails, MD2 completely fails. MD4 SHOULD now mark disk 1 (MD2) as faulty but does 
> not. Instead there is a dead-lock. "sync" hangs as well. Had to
> reboot.

Sorry for the delay in replying.

I cannot reproduce this. disk '1' of md4 (which is md2) gets moved to
position '2' and marked faulty.

You are running a pure 2.6.10 kernel are you? no patches at all?
Any other details you could provide?


> 
> I am now using the native Raid 10. Is this stable enough?

Should be.... It hasn't had as much testing as raid1, but I'm glad you
are helping out by giving it a bit more....

NeilBrown


> 
> Best regards,
> Chris - RapidTec