I've had four dual-drive RAID enclosures for RAID mirroring. I've never had a single drive in these enclosures to fail, but I've had several controller board failures and have ended up cannibalizing the drives for other purposes. I finally discovered (and should have known for years) that macOS can turn any two same-sized drives into a RAID 1 mirror array (or RAID 0, JBOD, or RAID 10). Two single desktop drives are considerably less expensive than buying a dual-drive unit, and if one goes bad they're cheap and easy to replace and rebuild.
I bought two of these Elements 4TB desktop drives to make into a RAID 1 array for Time Machine on an iMac. I didn't want the MyBook drives because I didn't want the automatic encryption as a matter of simplicity and reliability. I needed a couple of more USB ports than I had and didn't want to bottleneck my USB 3 hub, so I bought an Anker USB-C to 4 port USB-A 3.0 adapter, since USB-C's bandwidth can absorb in one port anything these 2 drives can produce. Unboxed everything, plugged it in; fired up Disk Utility, formatted each drive for Mac, went to RAID Assistant, chose the drives I wanted, chose RAID 1 and sat back. Time from start to finish: about 15 minutes total, including plug-in time.
So far this setup has worked flawlessly. These drives are cool and almost silent. Transfer rates are good, better than with the dual-drive enclosures. The price was excellent, far less than buying a dual-drive enclosure. We'll see how everything behaves over time. They have done Time Machine backups hourly for several years now without issues.
Addendum: it's 2024 now, and the dual raid drives have performed flawlessly. I'm about to buy another one to back up my wife's photography and have chosen this drive again because of its reliability.
| Hard Drive | 4 TB Portable |
|---|---|
| Number of USB 3.0 Ports | 1 |
