If the main disk in your Mac is a spinning hard drive, you should probably upgrade to a solid state drive. Swapping in an SSD is the cheapest way to make your old computer feel like a brand-new Mac. But for backups, and for lesser-used internal storage in a Mac Pro or iMac, a hard drive still gives you the best value. You will pay far less per megabyte of storage.
The problem is that hard drives are noisy as well as slow. If you’re used to enjoying the silence of an SSD-based computer environment, then those whirrs, whines clicks and pops will drive you nuts. Which is why you should unmount your noisy hard drives. That way they’re still available to the apps that need them, but otherwise they’re sleeping.
What is disk unmounting?
A connected drive can be in one of a few states: Mounted (when you’re using it), mounted but sleeping, unmounted or ejected. You can tell your Mac to put hard disks to sleep “when possible,” but in practice, this just makes things worse. Every once in a while, the disk’s motor engages, the disk spins up, and it starts clickety-clicking. It’s the computer equivalent of snoring.
If you eject a disk, then you’re done until you unplug it and plug it back in.
Unmounting is effectively just like ejecting, only the Mac can remount the hard drive when needed. The disk will never spin up. The Mac doesn’t even acknowledge its existence in any of the usual ways — it disappears from the Finder, for example. But apps can ask for it to be remounted. Backup app Carbon Copy Cloner, for example, can mount a disk, perform a backup, and then unmount the disk again. And as an added bonus in this case, this means that you’ll never accidentally delete anything from your backup.
How to unmount a Mac disk
Unmounting a Mac disk is easy. Just open up the Disk Utility (found in the Utilities folder inside the Applications folder), and take a look. Click on a disk in the left panel, and you’ll see the option to un/mount in the window’s toolbar. (You can also choose Mount and Unmount commands from the File menu.)
Or you can use the unmount command in the Terminal. It’s something like this:
diskutil unmount /dev/disk1s2
… where the
/dev/disk1s2 part is the name and path of the disk — you’ll have to determine that for yourself.
Hard drives prove ideal for backups
Once you have unmounted your Mac hard drive, you’ll have to mount it again to use it. That makes this tip most useful for backup disks, because you can a) use a clicky, slow, noisy-but-cheap HDD, and have it stay unmounted; and b) backup software can take care of the un/mounting all by itself.
If your backup HDD is driving you nuts with its incessant noise, this is the way to go. The only downside is that you will have to manually unmount the disks every time you restart your Mac. If you have any tips for that, let me know.