software RAID-1 question

Discussion in 'Mac Pro' started by initialsBB, Nov 12, 2011.

  1. initialsBB macrumors 6502a

    Oct 18, 2010
    Searching for this gave me lots of results that didn't answer my question, so here goes:

    I have a 2x2TB RAID-1 in my Mac Pro, and one of the drives is making a strange click sound. I'm not sure if it is seeking or what, but I was wondering if I could pull out one the 2 drives that makes up the RAID and boot the Mac Pro. If there is a drive failure, can I just put the one that still works into an external enclosure and copy it onto a new RAID ? They're Hitachi 2To Deskstar 64Mo S-ATA III 7K3000 drives which are very quiet, so I don't know if this noise is inherent to RAID-1 seeking or signs of a looming hard drive failure.

    Thanks for the help.
  2. Loa macrumors 68000


    May 5, 2003

    Soft RAIDs do not make any clicking sounds.

    Don't you have any back-up you could boot from and then be able to test the drives in your RAID?

  3. initialsBB thread starter macrumors 6502a

    Oct 18, 2010
    It's not my boot drive, so I can test them fine !
  4. deconstruct60 macrumors 604

    Mar 10, 2009
    RAID-1 means that the two disks have exactly the same data on them.

    You should be able to just remove the drive making noise and replace it with another drive. The RAID-1 implementation is pretty bad if it won't let you continue with just one disk. That is the whole point of having two copies; so you don't go down if just one fails. The RAID management interface should offer a way to rebuild the RAID 1 set.

    If this is a RAID-1 set built by Disk Utility here is how to do a rebuild.

    [ in newer Disk Utility versions there is a 'rebuild' button. Select the RAID in the disk/volume view. Select RAID tab. Should be an indicator that replacement drive is "failed" (or 'missing' if drive has been removed and not replaced) and a 'rebuild' button. ]

    if there is a failure you should remove the failed drive. The one that works should not be moved anywhere. You can run a backup to some other value while in that diminished capacity mode if you don't have a current backup. Moving the drive is likely only going to confuse the RAID software in some circumstances.
  5. nanofrog macrumors G4

    May 6, 2008
    The clicking, aka click of death, means the disk is on it's last legs, and needs to be replaced.

    As per what to do if it's created under Disk Utility, follow what deconstruct60 posted.

    I'd recommend making a backup of the set before doing any drive swaps, just in case you don't get it rebuilt properly (accidentally initialize the set rather than rebuild = wipes all data on the good disk currently in the set).

    And as mentioned, do not move the good drive in the RAID 1 volume. Software RAID implementations tend not to handle this very well (thinks the entire set is shot due to moving the disk, and issues messages that recommend the user reformat the good drive that was moved = existing data is wiped as it thinks it's a new disk installed in the system).

    It's usually possible to get it back via recovery software so long as no new data has been written to the disk (i.e. DiskWarrior), but it's not fun, and best not make that mistake to begin with. ;)

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