Setup Question for RAID1 in Disk Utility

[mslilyelise]

Hi folks. I'm looking at getting a secondary HDD to mirror the one we have setup on our media server, since if we lose the data on the primary drive it has no backup right now, and losing 5TB of archived DVD video would be painful. The server is run on an iMac with an external 8TB drive.

My question is, to set up a RAID1 configuration in Disk Utility, is it possible to start with one drive that has the data, add a second blank drive of the same size and configuration, and then get the system to rebuild the new drive with the data on the current one? Or do both drives need to be erased when creating the configuration? Need to know so I can borrow a third 8TB drive for that process if necessary.

The other option would be to buy something like a QNAP DAS and use their software to create the RAID1 array, as I believe it's capable of doing that, but that is a lot more expensive than buying an external enclosure with no RAID software or hardware. But if there's a benefit to doing it that way, by all means let me hear it.

Thanks for the help, as always.

 

[Brian33]

I'm looking at getting a secondary HDD to mirror the one we have setup on our media server, since if we lose the data on the primary drive it has no backup right now

My question is, to set up a RAID1 configuration in Disk Utility, is it possible to start with one drive that has the data, add a second blank drive of the same size and configuration, and then get the system to rebuild the new drive with the data on the current one? Or do both drives need to be erased when creating the configuration?

I have used Apple's Disk Utility RAID, but it was long ago, so I don't know the answer to your specific question. However, I'll offer an alternative idea...

If I understand correctly, what you want is a backup of your primary media drive, in case that drive fails. I suggest that using a backup utility to an inexpensive external HDD is a better solution than software RAID1. I'm most familiar with Carbon Copy Cloner (CCC), but there's also Super Duper (SD) and I'm sure others. Scheduling an automatic backup each night should be sufficient.

The advantage you can get with a real backup utility (besides simplicity), is the ability to go "back in time" to retrieve a file that has been accidentally deleted or discovered to be corrupt in some way. If the backup disk is larger than the amount of data actually backed up, then CCC will create snapshots on the backup disk that mirror the exact, full state of the source drive as of a particular moment in time. As many snapshots will be retained as will fit on the backup disk, and with APFS formatting of the backup disk, there are very clever mechanisms to use minimal space for each snapshot. So, with 5TB of media stored on an 8TB drive, you could easily restore any file (or all files) as they existed, probably, 6 to 12 months ago. Likely even more as your media files will not be changing much. If you do fill up your primary media disk, well, you'll have (at worst case) only one snapshot on the backup disk -- no worst than a RAID1 setup.

Also, in my humble opinion, a backup utility is likely to be more reliable than a software RAID setup. (I don't have any evidence at hand to support that, however.) I can't think of any advantage that the RAID-1 approach has, except you don't need to choose, and potentially pay for, a backup utility. CCC looks like it goes for $50. I have found it to be exceptionally reliable with superb support. Super Duper is about $28; I've never used it. There are probably free choices, as well.

The other option would be to buy something like a QNAP DAS and use their software to create the RAID1 array, as I believe it's capable of doing that, but that is a lot more expensive than buying an external enclosure with no RAID software or hardware.

Going with a standard backup utility like CCC or SD would just require a regular inexpensive external HDD. IMHO, a QNAP seems like more than what's needed.

Anyway, hopefully someone else can answer your Disk Utility RAID questions.