Re: raid0 not growable?

On Wed, Dec 23, 2009 at 10:45 PM, Neil Brown [off-list ref] wrote:

On Wed, 23 Dec 2009 13:52:54 +0000
Kristleifur Daðason [off-list ref] wrote:

quoted

Hi,

I'm running a raid0 array over a couple of raid6 arrays. I had planned
on growing the arrays in time, and now turns out to be the time.

To my chagrin, searches indicate that raid0 isn't growable. Can anyone
confirm this before I wipe and reconfigure?

That is correct, you cannot currently grow md/raid0.

If the two raid6 arrays are exactly the same size, then you
could grow the two raid6 arrays, create a new raid0 over them
with the same block size and all your data will still be there.
But if they are not the same size, that won't work.

NeilBrown

Many thanks for the reply. (Re-cc'd to the linux-raid list. Hope that's OK.)

1.
The raid6 arrays are exactly alike. Do I just do a create a new raid0
with the right size, device count and chunk-size parameters? I trust
your advice, but I am also certain of my own foolishness. I can't
fully picture what happens to the data on the array -- Specifically,
I'm thinking about whether to use --assume-clean or not. The
documentation says not. I am guessing that a newly-created raid0
doesn't do any syncing/resyncing anyway - it just sets up the array
structure and metadata and I am left to my own devices to fill it with
data.

Current chunksize is 256 and metadata is 1.1. So it's just a "mdadm
--create /dev/md_bigraid0 --level=0 --raid-devices=2 --metadata=1.1
--chunksize=256 /dev/md_raid6a /dev/md_raid6b", right?

2.
I have a JFS filesystem on the big raid0. Once I have the bigger raid0
built, I assume that I would first do a read-only fsck.jfs, which will
succeed if I did everything correctly. Then I do a remount with the
"resize" option to JFS to finally grow the JFS filesystem.

--

Sincere thanks. I hope I shall be able to contribute something
meaningful to mdadm when the company is richer and my time is freer :)
In the meantime, is there any preferred way of donating to mdadm or
sponsoring it?

-- Kristleifur
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