Disk Utility – Is RAID1 Volume Usable While Rebuilding RAID?

disk-utilityraid

One disk of my 2-disk-RAID1-stack has failed and I'm about to replace it.

Is the volume usable—i.e. can I read & write just as I normally could—while Disk Utility is rebuilding the RAID?

Best Answer

Yes, rebuilding happens in the background and the volume can be accessed normally.

I/O performance might be affected, but in my own experience it's more likely the rebuilding process that takes the performance-hit—i.e. rebuilding would be faster if the volume wasn't in use.

Related Solutions

Why does RAID 1 “Mirroring not provide performance improvements”

My guess would be that Apple prefers to have one drive handle only write processes as a backup and read/write from whichever one it considers the main drive. As to why this is, I have absolutely no clue. Seems kind of like a big oversight on their part. I've always kind of gotten the feeling that software RAID is pretty low on Apple's priority list.

Replace Failed Disk – How to Replace Disk in Disk Utility RAID 1

I was unable to find how to rebuild the RAID from disk utility after a couple of hours of research. However, I managed to do it from the command line.

sudo diskutil list  // to get a list of disks. Note the disk number of your new disk (e.g. disk4)
sudo diskutil appleraid list // note the uuid of the raid in question
sudo diskutil appleraid add member disk4 UUID-OF-YOUR-RAID

It will then kick you back to disk utility and start rebuilding the raid :)

Also, if the failed disk remains on the list, you can remove it:

diskutil appleraid remove UUID-OF-FAILED-DISK UUID-OF-RAID

Best Answer

Related Solutions

Why does RAID 1 “Mirroring not provide performance improvements”

Replace Failed Disk – How to Replace Disk in Disk Utility RAID 1

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