On Fri, Mar 12, 2010 at 3:39 AM, Patrick J. LoPresti [off-list ref] wrote:

From reading the documentation and source code, I gather "mdadm
--grow" is not supported for RAID-0 devices.

In my application, I am using md RAID-0 to stripe among several
(identical) hardware RAID-0 chassis.  I would like to extend my setup
by adding another chassis, but apparently, I cannot (?).

The next time I build a system like this, is there any way to get what
I want using Linux?  That is, striping among devices, no parity, but
with the ability to grow in the future?

I agree with others on the list - I believe that LVM will perform well
as a flexible stripe wrangler on top of mdadm arrays. For instance
some LVM striping over mdadm parity-based stuff underneath.

Do you want to add a whole new stripe device, so changing the
coarse-scale layout, or grow the underlying data containers?

I had a problem related to growing underlying containers which was
solved on the list a few weeks ago. I had two largish RAID6 arrays and
an mdadm stripe-set over those. I added some disks to both RAID6
subarrays and wanted to expand the stripe-array to use the space
gained. Here's a copy of the thread, "raid0 not growable?":
http://www.issociate.de/board/post/501375/raid0_not_growable?.html

But perhaps you wanted to do something like add a 3rd stripe to a
two-stripe array? (I myself don't know if that's possible or not.)

As you are running striped, I assume that the data is either
perishable or backed up. I'd suggest you look into moving to LVM. (LVM
has its quirks - so look before you leap, perhaps :) ) I suggest you
play a little with LVM in a virtual-machine; In the gas-lit and
magical world of open-source RAID management, there's nothing like
direct experience to tell you what's possible and what doesn't work.
The tools and the power are out there, but you have to do a little
hunting in the forest.

Best of luck!

-- Kristleifur
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