Re: Is shrinking raid5 possible?

[Thomas Arthur Oehser <tom@toms.net>]

On Fri, Nov 06, 2009 at 06:32:15PM +0000, John Robinson wrote:
> On 06/11/2009 13:17, Thomas Arthur Oehser wrote:
> [...]
>>  - resize2fs /dev/md3 <smaller>
>>  - mdadm -G -z <smaller> /dev/md3
>>  - fdisk /dev/sd[a-c]3 <smaller>
>>
>> It _almost_ works fine... but... the mdadm -G keeps the (0.90) superblock
>> at the _end_ of the _device_ ... which hasn't been resized yet ...
>>
>> How do I put the superblock back after fdisk, or make -G move or recreate?
>
> Are you sure it hasn't already put a copy of the superblock in the right  
> place, within the <smaller> size, as well as leaving a copy at the end  
> of the original larger partition? That's what I would do if I was the  
> author, so the partition can still be recognised as a md one before the  
> partition is resized; you wouldn't want the parition to become  
> unrecognisable or unusable.

Far as I can tell, no, because when I then shrink the partition, it can't
find the superblock.