Make your own Drobo for cheap. Well, not exactly. But close. If you are like me your main drive is 3T or bigger now. You also probably have a bunch of 1T drives laying around. Some you can use for particular manual backups. However you can’t really use them for automated backup because they are just too small. Like me you may have looked at Drobos or Synology bays with lust, wishing you could take your old drives and make a backup system with them. Yet those drive bays are ridiculously expensive.
The alternative is to use Apple’s Fusion Drive technology. You won’t be creating an SSD/HD fusion.1 Rather you’ll be taken a bunch of drives and treating them as a single logical drive. To avoid things from getting too confused, I strongly suggest getting a multidisk bay. I used a ProBox USB3 4 bay enclosure for mine. If you don’t do that remember that if one drive goes down none of the drives will work right. In other words bad things happen if they aren’t all running. Trying to keep 4 disks straight when you may have several others is just asking for trouble.
The way to creation the fusion drive is to first unmount (eject) all the disks you plan on combining. Next run diskutil from the command line. (The GUI version doesn’t yet support Fusion Drives) Then list all the drives so you can get their disk numbers by
You should be able to find the names of the drives you ejected. Each one will have a disk number akin to /dev/disk10.
Next we create the fusion drive by putting all the disks you found in the previous step in the following command. My disks were disk08 through disk11. You’ll almost certainly have different numbers. But I’ll put my command line here. Replace FusionTM with a name of your own choosing for the logical volume.
diskutil coreStorage create FusionTM /dev/disk11 /dev/disk10 /dev/disk9 /dev/disk8
When the command is done diskutil will give you a new Logical Volume Group with an associated UUID. Copy that number. It’ll be something like B65C4713-6C5D-40F4-A2D3-7698F90D7A79. Next we’ll create the actual disk. Replace the UUID in the below with the one you got from creating the logical volume. In place of “SpanTM” put a name for your disk. (This is the name it’ll have in the Finder when mounted. If you don’t want it to use 100% of the volume try a smaller number.
diskutil coreStorage createVolume B65C4713-6C5D-40F4-A2D3-7698F90D7A79 jhfs+ SpanTM 100%
Congratulations. You’re done. Your new disk should be mounted in the Finder. If you are using old disks, make sure you don’t use this as your primary backup. I use it as a reserve Time Machine backup myself. (Time Machine seems to only work reliably when its disks are at least 1.5x as big as your main drive — so this is an easy way to set one up if your boot drive is big)
As I said, it’s not exactly like a Drobo. You can’t take a single disk out, replace it with a larger drive and have everything work. That’s where Drobo excels. However if you were eyeing a Drobo just to make use of your older drives this is a cheap and easy way to do it. The enclosure I used only cost $90 and I had all the drives already sitting around.
- Although that’s pretty easy and works great. I put a 420G SSD in my 2010 MBP along with a 500GB 3.5” HD. Works fantastic. ↩