[Discuss] automation for installing to or converting to RAID

[Rich Pieri]

On Mon, 03 Dec 2012 13:57:34 -0500
Tom Metro <tmetro+blu at gmail.com> wrote:

>   Raider is a tool to automate linux software raid conversion.
>   It is able to convert a single linux system disk in to a software
> raid 1, 4, 5, 6 or 10 system in a two-pass simple command.

From my brief skim, it looks like Raider doesn't actually convert a
file system or device to RAID. It generates a new RAID metadevice with
mdadm, clones the original to the new MD, then turns the original
device into a replica. This is a reasonable way to do it.


>   The problem is that installing Linux onto a RAID array is
> non-trivial. None of the major linux distributions include an easy
> way to install Linux with RAID.

I disagree with the statement entirely because it is wrong. The
mainline kernel has supported 3Ware RAID controllers since Debian
Sarge if not earlier. 3Ware RAID sets are just big disks as far as the
installers are concerned.

Now, if they had presented it as "installing Linux onto a software or
fake RAID array" then I'd have bought it. Setting up the devices is a
hassle.

I still think that btrfs has is the easiest of all. Just two commands.
You can do it on a live system. Assuming that you have /dev/sdb as the
existing device, /dev/sdc as the new device, and /mnt as the root of
the volume and you want to create a mirrored set:

# btrfs device add /dev/sdc /mnt
# btrfs balance start -dconvert=raid1 -mconvert=raid1 /mnt

Sit back and let it do its thing. I'm really liking what btrfs has done
and where it's going. It's doing all of the cool things AdvFS did 10
years before ZFS happened. AdvFS is still my favoritest file system
evar but Butter is getting close to surpassing it.

-- 
Rich P.