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I have a linux server (running Ubuntu 12.04 Server currently) that I need to set up multiple hard drives of differing sizes in primarily for media/backup purposes.

The sizes are:

  • 1x2TB
  • 1x1TB
  • 2x500GB
  • 2x3TB

And I'll probably add more at some later date.

I've set up quite a few servers in the past running software RAID1 across only two disks, which works well, but they were always the same size and couldn't be expanded anyway, so RAID1 was the right option.

Here I have been reading up on LVM and/or LVM2, and from what I can tell I have quite a few options, some of which I can think of are:

  1. put RAID1 at lowest level, partition 2TB drive to 1x1TB, 2x500GB partitions
    • mirror the 2x3TB together /dev/md0
    • mirror 1TB and 1TB partition on 2TB drive /dev/md1
    • mirror 500GB and 500GB partition on 2TB drive /dev/md2
    • mirror 500GB and 500GB partition on 2TB drive /dev/md3
    • I can then:
      1. use LVM to combine /dev/md* to a single volume and put my filesystem on that
      2. format and mount them all separately, then use unionfs-fuse to present a single 'view' of them
  2. LVM(2?) group all the drives with mirroring enabled (not actually sure how to do this)
  3. LVM group the smaller ones and put RAID1 over top of it (I've seen people say mdadm over LVM isn't advised, but no reasons why)
  4. RAID0 the smaller ones and put RAID1 over top of that

For a filesystem I'd probably go with ext4 by default, unless there is a reason to go with something else.

Can anyone give me some ideas or pointers in the right direction? Thanks!

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Replace the 1TB with another 2TB. Setup several RAID1 volumes add them all to LVM? –  Zoredache Nov 30 '12 at 16:50

2 Answers 2

I'd try to get drives of the right or similar sizes... Why complicate things?

What is your actual storage requirement? If it's less than 3TB, then a mirror of 3TB disks is the path of least-resistance.

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I have ~3.5TB of data right now, and it's expected to grow in the future. I just bought the 2x3TB drives, and my data currently lives on the other ones (in addition to a 300GB IDE drive I'm pulling). I certainly wouldn't buy drives of these sizes, but it's what I'm stuck with using for now. –  moparisthebest Nov 30 '12 at 14:10
    
Can you just purchase another 3TB disk (well, two) and plan for a RAID 1+0 setup? That gives you 6TB usable and avoids the ugliness of using software RAID across partitions. –  ewwhite Nov 30 '12 at 15:40
    
Ultimately I'd like to do that, but for now this is the setup I'm stuck with. I'll be using software RAID (mdadm) for all my RAID setups anyway. –  moparisthebest Nov 30 '12 at 15:55
up vote 0 down vote accepted

I ended up going with option 1.1, RAID1'ing all of the smaller drives and then combining them all with LVM. That gives me the option to easily grow later, which I don't believe RAID0 would do.

All the options given by comments and answers certainly would have been better, but all avoided the original question by buying extra hard drives and doing away with current ones, which isn't a possibility at the moment.

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