New to software RAID, need some advice

Discussion in 'Mac OS X Server, Xserve, and Networking' started by maghemi, Jan 31, 2010.

  1. macrumors 6502

    I'm looking into getting myself a server setup of some description. Such as a Mac Pro or xserve with external storage.

    I've got a number of 1tb drives at the moment and a 4bay external drive that hooks up using esata.

    I was thinking of getting another 2 2tb drives and putting 2x 1tb and 2x 2tb drives in the enclosure and setting up a RAID 1.

    Would it work with those drives to get 3tb of actual storage (ignoring the real formatted capacity for a second) from those drives in RAID1. or do all drives in a RAID 1 set have to be the same size?

    It's got me a bit confused.
  2. macrumors member

    2 volumes


    You can put all of these drives into RAID 1 configurations, but it will be 2 different volumes.

    i.e. the 1TB drives will be one mirror set and the 2TB drives will be another.

    You will get 3TB of storage but in the form of one 1TB volume and one 2TB volume.

    Hope this makes sense.


  3. macrumors 6502


    Ahh k, so it wouldn't work as a single volume.
  4. macrumors member

    No single volume


    No, you wouldn't get a single volume.

    To achieve that using normal RAID techniques, all of the drives would need to be the same size, then you would configure them in a RAID 1 + 0 or RAID 10 configuration where the data is striped (RAID 0) across mirrored volumes (RAID 1) or vice versa.


  5. macrumors newbie

  6. macrumors 6502a


    Once you've created the 1TB and 2TB raid 1 sets it occurs to me that it might be possible to concatenate both raid sets into what would appear to be a 3 TB volume. Having had a quick play in Disk Utility on Snow Leopard it looks like a possibility although I didn't execute it so can's say for sure.

    Once you have the two RAID 1 sets online, go into the RAID setting on disk utility again, press + to add another one, set the drop down to concatenated then drag both of your RAID 1s into the new concatenated set icon.

    Like I said, not 100% certain, so let me know how it goes.

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