Raid - 2x different capacities?

Discussion in 'Mac Pro' started by steveOooo, Nov 4, 2011.

  1. steveOooo macrumors 6502a

    Jun 30, 2008
    If I put a 2tb and 1 tb drive in and format as raid 0 (so 3tb raid) is this ok as there different capacities . Or do I have o use 2 x 1 or 2 tb drives?
  2. Catch macrumors 6502

    Sep 22, 2004
    London, UK
    afaik you need to use same size drives for soft raid under OSX... never did try though mind you, as I have always bought identical drives for any RAID stripes like that in the past. If its possible you would at the most get 2tb though...

    I am sure you will get a techie answer soon! :)

  3. thankins macrumors 6502

    Oct 25, 2007
    Previous poster is correct. For a RAID to work you have to have two of the same size drives (2 x 2 Tbs has)
  4. nanofrog macrumors G4

    May 6, 2008
    You can build a RAID set (hardware or software) from mixed capacity disks.

    However, the usable capacity of any set created from them will be based on the smallest capacity disk (JBOD is not actually a RAID level, and technically speaking, level 0 isn't either, as it's not redundant).

    So in your case of a 2TB + 1TB disk in a stripe set, the usable capacity is 2TB, not 3TB. You can gain access to that remaining 1TB by making a partition, but if you try to use it simultaneously with the RAID, you will see a performance hit.

    Hope this helps. :)
    Actually, it isn't. See above. ;)

    Most do use the same disks (identical model) in RAID configurations, particularly when starting out, but it's more common to see mixed sets in enterprise environments due to failed disks being replaced with something newer, or is in the middle of an upgrade (such as the set is undergoing Online Expansion or Online Migration).

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