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Recently I bought an SSD disk and started to back up. I did not remove the old backup disk from TM. I use both old backup disk and the new one randomly for backup. I thought Time Machine will ask for specific disk. but I did not notice any message. I wonder if I want to restore the whole system for full restore; both have the full backup, and can be used and perhaps only for latest changes it may need the other disk.
MacBook Air 13″, macOS 12.7
Time Machine will back up to as many backup disks you provide for its use, in "rotation". First one, then the next one, and so on. If one disk is unavailable it searches for the next one.
I wonder if I want to restore the whole system for full restore; both have the full backup, and can be used and perhaps only for latest changes it may need the other disk.
If you want to restore a backup, you get to choose which backup to restore. The disk it happens to reside on doesn't matter; just the backup date / time. Only the disk with that backup needs to be available.
For example if you want to restore the latest backup, and the disk with that backup does not happen to be connected when you want to restore it, connect it first. To be completely accurate, the latest backup is always on the source disk, which can also be restored if you wish. Those "local snapshots" are complete and fully restorable system backups. In that case you don't even need any of the external disks. Obviously if the reason for needing to restore a backup is to replace a failed source disk (startup disk) on a replacement startup disk or a replacement Mac, then it won't be available.
Probably more information than you wanted, but having more than just one Time Machine backup disk is a very good backup strategy.
In fact that's a very good strategy. There is no compelling need to have backup disks connected all the time. In fact, if lightning were to strike (literally) the ensuing damage could conceivably be fatal to the Mac as well as all all devices connected to it.
TM continues to create "local snapshots" on its own, all the time. A routine incremental backup will be created when a TM backup disk eventually becomes available again.
There is really only one valid reason to leave a TM disk connected all the time, and that's to preclude forgetting to connect it at all. TM will warn you about that but not until ten days have elapsed. This is how I use portable Macs. At least one backup disk is always geographically separated from the others. For desktops, at least one backup disk either travels with me or stays someplace else.
And if during restore i connect any of the two , TM will use the one that I connected to restore and if the latest changes are not there; at the end of the restore it will ask for the other disk?
It will search the connected disk for available backups. Each disk will contain, at a minimum, one completely restorable system backup, independent of any others. There will be no prompt for the other disk(s), nor will there be any need to.
Thank you John٫
I am preparing myself for disaster recovery; failed startup-disk or as you mentioned( in case of failed Mac or upgrade)to restore on the new Mac’s disk.
I do not connect both backup disks all the time. I randomly( not a good idea probably)connect one of the backup disks When I want to backup. I believe٫when a new backup disk is deployed, TM will create a full back up on the new backup disk, which means I will have a full backup on both backup disks and then based on which one I connected last, changes will be copied to that one. And if during restore i connect any of the two , TM will use the one that I connected to restore and if the latest changes are not there; at the end of the restore it will ask for the other disk?
Many thanks John, much appreciated,
two disks back up and restore process
