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RAID 1: What happens if I swap in a drive?

264 Views 2 Replies Latest reply: Nov 9, 2012 12:27 PM by l_elephant RSS
eliotic Calculating status...
Currently Being Moderated
Nov 8, 2012 8:31 PM

For backup and storage, I have a partitioned Lacie 2Big HD in a RAID 1 (mirrored) configuration with another hard drive in the same enclosure. I am wondering what will happen if I swap in a new drive for the second one. Does Disk Utility recognize that I want to mirror the full drive on the empty one, and not vice versa? In other words, am I risking losing my data on the first drive if I put a blank drive in the second bay of the Lacie?


The reason I am considering doing this is in order to carry a drive off-site, as a further back-up. I thought I might then on some regular schedule swap it back in and carry the other drive off-site, so that I always have a recent, though not completely current back-up elsewhere. Is that going to work? Thanks!

MacBook Air, OS X Mountain Lion (10.8.2)
  • Retired Engineer Level 4 Level 4 (2,710 points)
    Currently Being Moderated
    Nov 9, 2012 4:25 AM (in response to eliotic)

    I've never used Apple RAID but I would think if you remove the second drive and then run the system it will know the second drive is gone.  You may need to delete the partition on the new second drive before it will do a successful RAID rebuild.


    That said wouldn't it be simpler to use Carbon Copy Cloner to make an image of your system to the third drive.  I recommend at least two backup drives because at the instant you start a clone to a single drive you have no backup drive until the clone process is completed.

  • l_elephant Level 2 Level 2 (375 points)
    Currently Being Moderated
    Nov 9, 2012 12:27 PM (in response to eliotic)

    if you remove a drive from a RAID1 set, it will not just start copying the contents to a new drive that you pop in.


    it will do nothing. The RAID  set will just assume theyre separated and wait for you to put them both online again.


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