Hello list,
I've looked online a bit, but didn't really find the answer to the
following question.
While expanding an existing raid is as simple as mdadm --add, followed
by an mdadm --grow, How would you go about this when expanding it with
multiple devices.
A little bit of background. I have 8 2TB disks, 4 in a current raid5
array, which will be the donor disks en 4 'new' disk going to form the
basis of a new array. I want to change chunk size and re-format to ext4
to a) optimize the new array according to the new parameters
(stride,stripe-width) and (possibly) a new ondisk ext4 disk format (new
features added since last time). The old array was 4 disk raid5, the new
array will be 8 disk raid6.
So far, I have created a new raid6 array with the 4 'new' disks + 2
'missing' for the parity. I have done it this way, so that I would have
enough space to copy (and verify) files. having done a 4 disk raid6
without any missing devices, there would simply have not been enough
space. True I could have used 3 data disks, 1 parity and 1 missing.
Anyway, my plan next, is to expand the array. I can think of the
following options.
a) Remove 1 disk at a time from the old array, and add it to the new
array, first 2 disks would be parity, after that --growing the last two.
Big disadvantage is of course that there will be almost a week or two of
re-syncing going on.
b) Would be to somehow add all 'extra' disks at once, and have it rsync
it all in one go.
Any idea's how best to expand all this?
Oliver
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