Building a RAID post-mkfs?

Building a RAID post-mkfs?

[Chris Ball]

Hi,

I installed btrfs to one disk using the Fedora 12 installer; it
doesn't allow any configuration of the mkfs command by the user,
so it wasn't possible to mkfs with more than one disk.

I'd like to add a second disk, with either RAID0 or RAID1 between
the two -- the equivalent of "mkfs.btrfs -m raid0/1 -d raid0/1
/dev/sda /dev/sdb".  Is it possible to create this non-destructively
now?  If not, should it be?  What would the implementation look like?

Thanks,

- Chris.
-- 
Chris Ball   <cjb@laptop.org>
One Laptop Per Child

Re: Building a RAID post-mkfs?

[Chris Mason]

On Fri, Oct 16, 2009 at 01:54:10PM -0400, Chris Ball wrote:
> Hi,
> 
> I installed btrfs to one disk using the Fedora 12 installer; it
> doesn't allow any configuration of the mkfs command by the user,
> so it wasn't possible to mkfs with more than one disk.
> 
> I'd like to add a second disk, with either RAID0 or RAID1 between
> the two -- the equivalent of "mkfs.btrfs -m raid0/1 -d raid0/1
> /dev/sda /dev/sdb".  Is it possible to create this non-destructively
> now?  If not, should it be?  What would the implementation look like?

It's not very complex, you can take a look at how we upgrade from
single spindle dup to RAID1 for metadata when a second disk is added.
Basically once we have a block group with the new type we're able to
force new allocations to the new raid level.  btrfs-vol -b does the
rest.

-chris