mac os monterey 12.5.1

My external drive 2to is split into two partition of 1to

  • One called backup001: it is formated mac os, and it uses for timemachine for a long time. it works ok.
  • Another partition is called backup002thunder: it is used to be for formated exfat, but recently formated mac os to be used for timemachine as well.

The backup002thunder is mount/visible on my mac but NOT VISIBLE in timemachine to be selected as a backup destination. (but this partition is visible in option if i want to exclude the disk from timemachine)

WHY CAN T I SELECT THE DISK AS ANOTHER TIMEMACHINE BACKUP? (I have another external disk called thunder and that one is visible (formated APFS)

what I want:

  • backup001 1to: used the partition backup001 for internal SSD backup. it used to be like that. I want to keep it that way
  • backup002thunder 1to: I want to backup an external SSD (called here thunder) on that partition.

how can I do that?

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  • If backup001 is already used by TM, why do you want to add it again?
    – nohillside
    Jul 21 at 10:03
  • Having said that: If you select backup002 as a backup destination, your internal disk will get backed up to it. Is this what you want?
    – nohillside
    Jul 21 at 10:04
  • If you persuade Backup 2 then what you'll have is two sets of almost identical backups of all your drives on two partitions on the same physical drive. I don't see this as being any better or safer than just using the entire drive. You can't set both backups to have different sources anyway. BTW, you didn't tell us what macOS you're on. That may make all the difference. It looks like you're on Big Sur or newer, which would mean Time Machine wants an APFS-formatted drive to backup to.
    – Tetsujin
    Jul 21 at 10:19
  • I am using mac os monterey 12.5.1
    – polax
    Jul 21 at 15:12
  • 2
    Time Machine must be on an APFS-formatted disk for Monterey, not HFS+. You cannot make one disk back up to one Time Machine & another disk to another TM. Time Machine backs up everything in your allowed list to both drives. What you are attempting is not going to achieve what you want.
    – Tetsujin
    Jul 21 at 16:45

1 Answer 1


I'm afraid what you want is not achievable.

Firstly, the reason the Backup002 drive cannot be seen by Time Machine is that it must be formatted APFS to be used. HFS+ drives could be used on older macOS but not since big Sur.
Strictly speaking, t will allow to to continue to use an HFS+ disk if a Time Machine backup is already on it. It will not allow you to start a new one. - https://support.apple.com/en-gb/guide/mac-help/mh15139/mac

Secondly, you cannot set two different backup strategies for two Time Machine backups. This would mean Time Machine will simply make the same backup to each partition in turn, separated by an hour.

  • one of my partition is formated mac os (backup002thunder is formated the same way) not APFS and it is still visible from time machine. so it doesn t make sense for the second partition still not visible formated the same say. but for the your secondly, i get it. thanks
    – polax
    Jul 23 at 7:49
  • It will allow to to continue to use an HFS+ disk if a Time Machine backup is already on it. It will not allow you to start a new one. - support.apple.com/en-gb/guide/mac-help/mh15139/mac
    – Tetsujin
    Jul 23 at 7:52

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