On 13/03/14 00:18, NeilBrown wrote:

On Wed, 12 Mar 2014 13:45:31 +0100 David Brown [off-list ref]
wrote:

quoted

So for raid1, you would add a new mirror device, making a 3-way mirror
instead of a 2-way one (I don't know off-hand if md raid allows this
re-shape).

It sure does. raid1 can be 1-way, 2-way, 3-way, 4-way ..... and "mdadm
--grow" can easily switch between them.

I thought that was the case, but I didn't want to promise anything
without checking.

Thanks,

David