Re: Alex Samad Re: RAID5 (mdadm) array hosed after grow operation

On Thu, 8 Jan 2009 21:12:18 +1100, "Alex Samad" [off-list ref]
said:

On Wed, Jan 07, 2009 at 08:19:05PM -0800, whollygoat@letterboxes.org
wrote:

quoted

On Tue, 6 Jan 2009 09:17:46 +1100, "Neil Brown" [off-list ref] said:

[snip]

quoted

How should I have done the grow operation if not as above?  The only
thing I see in man mdadm is the "-S" switch which seems to disassemble
the array.  Maybe this is because I've only tried it on the degraded 
array this problem has left with.  At any rate, after 

    mdadm -S /dev/md/0

[snip]

quoted

Hope you can help,

Hi

I have grown raid5 arrays either by disk number or disk size, I have
only ever used --grow and never used the -z option

I would re copy the info over from the small drives to the large drives
(if you can have all the drives in at one time that might be better.

increase the partition size and then run --grow on the array. I have
done this going from 250G -> 500G -> 750g -> 1T. although when I have
done it, I fail one drive and then add the new drive, expand the
partition size and re add it back into the array, once I have done all
the drives I then ran the grow.

I'm not sure I uderstand what you mean.  When you copy the info over and
then increase the partition size, are you doing something like dd
if=smalldrive
of=bigdrive, then using a tool like parted to resize the partition?  

I put the large drives in (as hot spares) with a single raid partition 
(type fd) that uses the entire disk, so I can't increase their size any. 
Then when I failed the drive the data it contained was rebuilt to the
larger
hot spare.

But anyway, I don't think that is going to matter.  The issue I am
trying to 
solve is how to de-activate the bitmap. It was suggested on the
linux-raid 
list that my problem may have been caused by running the grow op on an
active 
bitmap and I can't see from "man mdadm" how to de-activate the bit map.

The only thing I see about deactivation is --stop and that disassembles
the
array, in which case I can't run the grow command.  I read how to remove
the bitmap, but then I guess I would have to readd it after the grow op.
 In
any case, I would like to get the figured out without too much
experimentation
because swapping drives in and out and rebuilding is pretty time
consuming so I 
would really like to avoid fudging this up again.

Thanks for you help

goat
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