Re: Test with raid 6 software

["Douglas A. Tutty" <dtutty@porchlight.ca>]

On Wed, Jan 30, 2008 at 01:52:49PM +0100, Pol Hallen wrote:
> I've 8 sata disk on raid 6 software (debian stable).
> 
> For purpose test I stopped 3 disks of the array.
              ^^^^
NOTE WELL: The md(4) man pages says that raid6 can handle the failure of
any 2 disks.  You pulled 3.  Good way to hose the array.
> 
> Now I rebooted and I tring to re-assemble the array but without successful..
> 
> mdadm -A /dev/md0
> mdadm: /dev/md0 assembled from 5 drives and 3 spares - not enough to 
> start the array.
> 
> cat /proc/mdstat
> 
> Personalities :
> md0 : inactive sdb[0](S) sdi[10](S) sdk[9](S) sdj[8](S) sdf[4](S) 
> sde[3](S) sdd[2](S) sdc[1](S)
>       3907091968 blocks
> 
> unused devices: <none>
> 
> Consider the data there are on the raid, and there aren't any disks 
> failure, is there a way to re-assemble the same raid and maintan the data?

Considering that this is a test, there should be no concern over data.
You did a backup prior to this test?

You hosed the RAID6 array by pulling 3 disks.  The spares only help if a
spare disk can get syncd before a third disk died.  

So, no, you have to make a new raid and restore from backup.

Doug.