Re: migrating raid-1 to different drive geometry ?

[Robin Bowes <robin-lists@robinbowes.com>]

Mike Hardy wrote:
> 
> I'd missed the mdadm --grow feature as well, so I checked into it.
> 
> It is only capable of increasing size on raid5, not component count. The 
> specific use case used as an example is that you slowly retire component 
> drives and the replacements are larger. When all components are the 
> larger size, you can grow the raid5 array to use the full size of the 
> device, followed by a filesystem expansion to use the grown array.
> 
> That makes sense, given the disk layout of raid5 - its not hard to add 
> more stripes on the end of components, but adding new components 
> requires each stripe to change significantly.
> 
> To grow component count on raid5 you have to use raidreconf, which can 
> work, but will toast the array if anything goes bad. I have personally 
> had it work, and not work, in different instances. The failures were not 
> necessarily raidreconf's fault, but its not fault tolerant is the point, 
> as it starts at the first stripe, laying things out the new way, and if 
> it doesn't finish, and finish correctly, you are in an irretrievable 
> inconsistent state.
> 

Bah, too bad.

I don't need it yet, but at some stage I'd like to be able to add 
another 250GB drive(s) to me array and grow the array to use the 
additional space in a safe/failsafe way.

Perhaps by the time I come to need it this might be possible?

R.
-- 
http://robinbowes.com