Time Machine stores hourly backups for 24 hours, daily backups for the past month, and weekly backups for all previous months for as much space as you have on your Time Machine backup drive. You also can use your Mac with more than one Time Machine backup drive.
Which Storage Devices Can be used with Time Machine?
Time Machine supports any of the following external storage devices.
External drive connected to your Mac, such as a USB, Thunderbolt, or FireWire drive
External drive connected to an AirPort Extreme Base Station (802.11ac model) or AirPort
Time Capsule (See our post, What’s the Diff: Time Machine vs. Time Capsule)
AirPort Time Capsule
Mac shared as a Time Machine backup destination
Network-attached storage (NAS) device that supports Time Machine over SMB
After you have configured iCloud drive Time Machine and iCloud Dive complementary to one another: iCloud Drive tracks the last 30 days of changes to your files, for example, while Time Machine will keep track of as many changes as it can within the storage capacity of your backup drive. So it’s nice — ideal, really — to have both. Better yet the data stored in iCloud is synchronized across all you devices that are signed into the same account.
Use More than One Backup Disk Using Disk Rotation
Time Machine handles disk rotation with aplomb. You can attach a second hard drive and use it with Time Machine with only a couple of clicks. When Time Machine is connected to your first backup drive, it will back everything up. Then it’ll do the same for the second one. Time Machine backs up everything that’s changed on your Mac’s hard drive since the last time that backup drive was connected. So each drive will keep a complete Time Machine backup.
How to Use Multiple Backup Drives with Time Machine
Connect your second hard drive to your Mac.
Click on the Time Machine icon in the menu bar, then click on Open Time Machine preferences.
Click Select Disk.
Select the drive you want to rotate, then click Use Disk.
Time Machine will ask you if you want to replace your existing Time Machine drive, or use both drives. Click Use Both.
Time Machine will now back up to each individual drive as they’re connected.
When you want to check on your Time Machine backups later, all you need to do is hold down the option key when clicking on the Time Machine icon in your menu bar. You’ll see Browse Other Backup Disks. You can use that to browse whichever Time Machine backup you’d like.
The same process works if you mix a Time Machine backup drive with Apple’s Time Capsule network device (a home Wi-Fi router with built in backup drive). You can back up to both without any problem.Using this procedure, your data is backed up on two (or more) drives.
You can leave one at home and take the other one with you on a long trip or for safe storage outside the house. For example. That way you’ll never be without a backup you can recover from quickly and easily.
Other Time Machine Backup Tips:
To exclude items from your backup, open Time Machine preferences, click Options, then click the Add (+) button to add an item to be excluded. To stop excluding an item, such as an external hard drive, select the item and click the Remove (–) button.
If using Time Machine to back up to a network disk, you can verify those backups to make sure they’re in good condition. Press and hold Option, then choose Verify Backups from the Time Machine menu.
In OS X Lion v10.7.3 or later, you can start up from your Time Machine disk, if necessary. Press and hold Option as your Mac starts up. When you see the Startup Manager screen, choose “EFI Boot” as the startup disk.