Swapping drives in a RAID 1 setup

Discussion in 'Mac Pro' started by CoffeeMonkey, Jul 26, 2011.

  1. CoffeeMonkey macrumors regular

    Joined:
    Feb 23, 2003
    #1
    I see that Amazon has a nice sale on the 2GB Western Digital Caviar Green drives, and I was thinking about switching them out for the two 1TB drives I am currently using in a RAID 1 setup.

    As I understand it, the drives in a RAID 1 setup are mirrored. So if I want to switch them out, would I switch one of the drives, wait for the two drives to be synched, and then shut down and switch out the second drive?

    Also, how can I tell when the two drives are synched?

    Thanks!
     
  2. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #2
    Generally speaking, Yes. But there can be issues with software implementations. So the best advice I can offer, is make a backup first.

    Usually, the process is as follows (if Online Expansion Feature is not automatic, as is usually the case with hardware RAID controllers).
    1. Pull one of the existing disks.
    2. Replace it with a new disk.
    3. Wait for the rebuild to complete.
    4. Swap out the other disk (last remaining original model).
    5. Wait for that one to be rebuilt.
    6. At this point, it's normal, but the capacity is only half (still based off of the original drives' capacity <or smallest if the disks weren't identical>).
    7. Change the available capacity to use all of what's now currently available (change it from 1TB to 2TB in this case).

    But it's actually easier IMO (particularly with a software controlled array), to do the following:
    1. Make the backup.
    2. Pull both of the original disks (completely remove the existing RAID 1).
    3. Install the new pair of disks, and create the RAID 1.
    4. Restore the data from the backup.

    If the RAID 1 is a boot drive, then clone it to a single disk if possible. Then make the clone the boot location, and perform the second, simpler implementation. Once done, then set the RAID 1 as the boot location again. Much easier IMO.

    Now on the off chance, this is on a hardware RAID controller that supports online expansion, it follows the first set of procedures, and most, if not all, is done automatically. Much easier than doing it all manually. ;)

    Check Disk Utility if it's done via OS X (you're looking for mounted/normal).

    If it's a hardware RAID controller, the status will indicate NORMAL.
     

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