On Fri, Dec 21, 2012 at 01:16:59PM -0500, Gene Czarcinski wrote:

I am new at this btrfs stuff!

As I understand it, you can add a physical disk or partition and
have data spread into the new space.  You can also move data off a
disk or partition and then remove it.

Has any though  been given to being able merge to existing
(separate) btrfs "volumes" into a single volume?

   This would be difficult to do in kernel space -- you'd have to
change the UUIDs on all the metadata on at least one of the
filesystems, plus handle (correctly) all of the numberspace clashes
correctly -- subvolume trees, virtual address space, and probably a
load that I've forgotten as well. Given what I'm about to say, I can't
see this happening any time soon.

Alternatively, how about at tool for transfering a subvolume from
one pool to another?  I tried using fsarchiver but that did not work
out too well.

   You want send/receive. It's in the mainline kernel, and you'll need
a recent userspace, but it allows you to transfer subvolumes cleanly
and losslessly between filesystems.

   Hugo.

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