RE: Help recovering from failed disk on RAID 6

["Steve Fairbairn" <steve@fairbairn-family.com>]

Hi,

It appears noone else has answered, so I'll try.  First I'd attempt to
start the array with the --force parameter, which I believe will start
the dirty array without the failed drive in it.

The other option to try depends on how long you have before the OS
freezes, but is to start the array with the dodgy drive in it, but
immediately tell mdadm to fail the dodgy disk.  This should have mdadm
start a resync with the spare drive.

Hope this helps,

Steve.

> -----Original Message-----
> From: linux-raid-owner@vger.kernel.org 
> [mailto:linux-raid-owner@vger.kernel.org] On Behalf Of Joshua Johnson
> Sent: 28 April 2008 03:17
> To: linux-raid@vger.kernel.org
> Subject: Help recovering from failed disk on RAID 6
> 
> 
> I am running a linux server with an 8 disk IDE/SATA RAID 6 
> array.  One of the disks is having a problem which caused the 
> machine to freeze. If I boot the machine without the problem 
> disk the array fails to start.  If I boot with the problem 
> disk the array starts correctly and begins syncing, but the 
> machine will soon freeze up again when the disk drops out.  
> My number one question is how to get the array back online.  
> It has a spare disk, but since the OS is freezing rather than 
> failing the disk that is having the problem, it never 
> switched to the new disk.  When I try to start the array 
> without the problem disk, I
> get:
> 
> #mdadm --manage --run /dev/md0
> raid5: device hda2 operational as raid disk 0
> raid5: device sdb2 operational as raid disk 7
> raid5: device sda1 operational as raid disk 6
> raid5: device hdi2 operational as raid disk 5
> raid5: device hdg2 operational as raid disk 3
> raid5: device hde2 operational as raid disk 2
> raid5: device hdk2 operational as raid disk 1
> raid5: cannot start dirty degraded array for md0
> RAID5 conf printout:
>  --- rd:8 wd:7
>  disk 0, o:1, dev:hda2
>  disk 1, o:1, dev:hdk2
>  disk 2, o:1, dev:hde2
>  disk 3, o:1, dev:hdg2
>  disk 5, o:1, dev:hdi2
>  disk 6, o:1, dev:sda1
>  disk 7, o:1, dev:sdb2
> raid5: failed to run raid set md0
> md: pers->run() failed ...
> mdadm: failed to run array /dev/md0: Input/output error
> 
> /proc/mdstat contains:
> Personalities : [raid1] [raid6] [raid5] [raid4]
> md1 : active raid1 hdg1[1] hda1[0]
>       4200896 blocks [2/2] [UU]
> 
> md0 : inactive hda2[0] sdc2[8](S) sdb2[7] sda1[6] hdi2[5] 
> hdg2[3] hde2[2] hdk2[1]
>       1529265920 blocks
> 
> 
> So how do I get this array to run?  I can't start it without 
> the problem disk and I can't sync it with the problem disk.  
> I am running RAID 6 to be able to recover from multiple disk 
> failures so it is a little vexing that a single disk going 
> offline renders my array unrunnable.  Any help with this 
> issue is greatly appreciated.
> --
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