Use Time Machine on your Mac to back up to multiple disks
For extra security and convenience, you can back up to multiple disks. If you work in two locations, you may want to keep backup disks in both places.
Time Machine rotates the backup schedule among the disks. For each disk, Time Machine backs up everything that’s changed since the last time that disk was used. If you designated items that shouldn’t be backed up, the list of excluded items applies to all backup disks.
If you use multiple backup disks, you can see timelines for all disks or for an individual disk.
To see a timeline for all backup disks: Click the Time Machine icon in the menu bar, then choose Enter Time Machine.
To see the timeline for a specific backup disk: Click the Time Machine icon in the menu bar, press the Option key, then choose Browse Other Backup Disks.
Note: If you create a backup on a Mac or partition with macOS Big Sur, you can only use that backup on Mac computers or partitions with macOS Big Sur.