Arch Linux

ngoonee

Forum Fellow

From: Between Thailand and Singapore

Registered: 2009-03-17

Posts: 7,358

RAID1 with differently sized discs - use additional space?

I've got a 500 GB external HD and another 650 GB one sitting round unused.

Been using both for backups (each in different locations), but now I have an additional 1TB external I plan to combine these into a single backup.

Obvious idea would be a RAID1 for more redundancy. Seems a pity to have an extra 150GB sit around though, would it be possible to do a raid1 with /dev/sdb1 and /dev/sdc1 (assuming sdc is the larger disc) and then use /dev/sdc2 as a separate partition?

Never used RAID before, and the 'multi disc' info I could find online suggests not (but they're mainly talking hardware raid best as I can tell).

Side-note, I've read about BTRFS' raid-like capabilities but seems a bit too complex for my liking for now, unless it would make the above possible where it wouldn't be with normal mdadm.

---

Allan-Volunteer on the (topic being discussed) mailn lists. You never get the people who matters attention on the forums.
jasonwryan-Installing Arch is a measure of your literacy. Maintaining Arch is a measure of your diligence. Contributing to Arch is a measure of your competence.
Griemak-Bleeding edge, not bleeding flat. Edge denotes falls will occur from time to time. Bring your own parachute.

fukawi2

Ex-Administratorino

From: .vic.au

Registered: 2007-09-28

Posts: 6,230

Website

Re: RAID1 with differently sized discs - use additional space?

There's no reason you shouldn't be able to do that; just make sure the partition dimensions of sd{b,c}1 are identical. Of course there will be a performance impact, but for your usage I'm guessing not significant enough to worry about.

Last edited by fukawi2 (2013-09-18 01:12:22)

---

Are you familiar with our Forum Rules, and How To Ask Questions The Smart Way?

BlueHackers // fscanary // resticctl

ngoonee

Forum Fellow

From: Between Thailand and Singapore

Registered: 2009-03-17

Posts: 7,358

Re: RAID1 with differently sized discs - use additional space?

Thanks fukawi, will add another partition after my /dev/md0 finishes syncing (this is taking AGES). And no, performance isn't a primary concern at all.

A bit disconcerting for me (being very used to gparted) that it doesn't show the btrfs filesystem I've created on /dev/md0, but since it looks otherwise accessible I haven't really bothered.

---

Allan-Volunteer on the (topic being discussed) mailn lists. You never get the people who matters attention on the forums.
jasonwryan-Installing Arch is a measure of your literacy. Maintaining Arch is a measure of your diligence. Contributing to Arch is a measure of your competence.
Griemak-Bleeding edge, not bleeding flat. Edge denotes falls will occur from time to time. Bring your own parachute.