Will one drive from RAID1 enclosure mount directly in Mac Pro?
October 24, 2020 8:51 AM   Subscribe

I have one open slot in my Mac Pro & would like to install larger drives in my external RAID 1 enclosure, then copy the files from one of the old drives. Is it that simple?

I have a Newertech "Guardian Maximus" drive configured in RAID1 that is full. Can I take one of these drives & have it mount like normal in the one spare slot I have inside my Mac Pro cheese grater?

What I want to do is put larger drives into the RAID1 enclosure, then copy all the files from one of the old smaller drives to the new ones in the RAID1 enclosure, but without having to buy a new enclosure. Is this possible or will the RAID controller have rendered the individual disks unable to mount directly as regular volumes when plugged into a Mac Pro SATA slot?
posted by Devils Rancher to Computers & Internet (8 answers total)
Best answer: This makes it sound like the answer is yes, one disk of a RAID mounted is still a degraded RAID. Obvs keep in mind that reading the entire contents of a disk back to front is something that can kill it. But hey, you have a spare.
posted by supercres at 9:13 AM on October 24, 2020 [1 favorite]

Best answer: I would recommend copying the old files onto one of the new drives, and then building a raid1 array around both new drives using the data you copied. This procedure ensures that your old data is always stored redundantly, lowering risk.

Often you can set up a raid1 based on data on an existing drive, so you can probably just copy the existing data on to one new drive and then build a raid 1 around it, and that is the preferred approach. If your particular enclosure can’t do that, it should also be possible to set up a raid1 array on the new drives on the Newertech enclosure, pull both drives out, put the two old drives back in the array and put one of the new drives in the Mac, copy the files, then swap back and rebuild.
posted by doomsey at 9:25 AM on October 24, 2020

Also, it may be possible to do a rebuild-rebuild sequence swapping one drive and then the other to resize your array on the fly. This is also reasonably safe.
posted by doomsey at 9:27 AM on October 24, 2020

Response by poster: Thanks! Also just got this (after waiting an hour for a connection) from OWC: "Yes. A drive removed from the Guardian MAXimus in a RAID 1 mirror would be able to mount when connected separately from the RAID enclosure.
That way you can remove the original drive with the data, install the two new drives setting up the Mirror. Lastly, copy the data from the original drive to the new RAID volume."

Follow-on question. If I don't/cant rebuild the array (I have seen some info suggesting that the new drive will end up with a partition the same size as the old drive)
This is a Time Machine. What's the best way to clone a time machine? CCC won't do it & the Finder seems unreliable, despite drag & drop being Apple's official method. Do I just grin & bear it?
posted by Devils Rancher at 10:07 AM on October 24, 2020

Try SuperDuper, they claim to support it and I’ve always had good luck with it. The free version should be able to do this.
posted by doomsey at 10:18 AM on October 24, 2020 [1 favorite]

Response by poster: Thanks, forgot about Super Duper.
posted by Devils Rancher at 10:20 AM on October 24, 2020

>This is a Time Machine. What's the best way to clone a time machine?

They're sparse disk images on HFS Plus filesystems. You can move them around like ordinary files if you mount the parent partition. It's probably a good idea to have a spare offline emergency ultra-safe copy, pages like Gruby (e.g. here for repairing a time machine backup) suggest cloning with CCC or similar for a cold, offline recovery option.
posted by k3ninho at 3:02 PM on October 24, 2020

RAID is not backup. RAID provides operational reliability. You should not do anything to your RAID without backing it up first.
posted by Area Control at 7:53 PM on October 24, 2020 [2 favorites]

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