On Tue, Oct 29, 2013 at 2:45 PM,  <tclug at freakzilla.com> wrote:
> Ok, so right now I have a RAID5 array I created with mdadm. It uses four
> identical HDDs, one of which is a spare obviously (which is good because I
> had one fail).
>
> Anyway, sincethe enclosure I use can support 8 drives, I'm getting four more
> HDDs (also identical to the first) and plan on adding them to the current
> array.
>
> Now my hopefully silly question is, do I have to do anything special while
> adding them, or does mdadm/whatever know which to add as "live" data and
> which to add as spares? Can I just go "mdadm --add /dev/md0 /dev/sdf1" (and
> then sdg1, sdh1 and sdi1)? Or do I have to do anything special?

when you do that you will add those drives as spares, you will then
have to restripe using something like:
mdadm --grow /dev/md0 --raid-devices=4  (since your raid deviced is currently 3)

and while you can probably go directly to 7, or 8 i would recommend
being patient and doing it one at a time.