I have 3 USB disks all doing Time Machine backups.

MacOS does them in series. Disk1, then Disk2, then Disk3, then back to 1 and so.

Sometimes it takes 4 hours to return to Disk1. Is there a way to make Disk1 the preferred disk or to make the cycle go faster?

  • What do you mean with "preferred" disk? Do you want TM to backup to Disk 1 twice as often as to Disk 2 and 3?
    – nohillside
    Nov 23 at 16:01
  • Why 3 always connected disks?
    – Gilby
    Nov 23 at 22:20
  • @nohillside - exactly
    – Duck
    Nov 24 at 12:55
  • @Gilby paranoia...
    – Duck
    Nov 24 at 12:56
  • I have made an answer below which answers your question (in the negative) but then make suggestions to feed the paranoia :)
    – Gilby
    Nov 24 at 21:35

1 Answer 1


This is an answer in two parts. Firstly to the explicit question about Time Machine (TM), and secondly some suggestions to a backup paranoid.

A gentle paranoia about backup is good thing so long as it addresses all data risks and mitigates them.

No, there is no way to make one TM disk have priority. TM is designed to have minimal configuration yet meet the needs to most users. It does not offer the kind of tweaks that many of us crave. That is the answer done.

Here are some comments on @Duck's current strategy and suggestions (opinions) for changes based on my experience.

Whilst @Duck is using 3 permanently connected disks to mitigate the risk of failure of a single backup disk, it does not address other risks like failure of TM software or major disasters like fire or theft. Also TM is designed to be as efficient as possible with repeated backups to one disk - it is less efficient with overlapping 3 hours cycles.


  • Continue to use Time Machine backing up to just one disk. Use an alternative product for backup to another disk on a 1 or 2 hour schedule. I would choose Carbon Copy Cloner (CCC) as the alternative. Both TM and CCC provide reasonably fast recovery following minor (but quite likely) local hardware disasters. I would use the third disk for something else.

  • Develop a strategy for off-site backup to mitigate the risks of fire, theft and other more life-catastrophic disasters. Off-site backup is also a mitigation strategy for ransomeware and other malware which corrupts local storage.

  • Off-site backup could be using the the third disk, but keeping it at a friend's home, workplace or bank vault. But keeping to a strict schedule of taking and storing these backups is not easy.

  • Instead, backup into the "cloud" using another backup product. I use the backup product Arq Backup with cloud storage from OneDrive ("free" with my Microsoft/Office 365 subscription) and Backblaze B2. Recovery from the cloud will not be fast, but after personally catastrophic disasters this is not critical.

Develop your own risk based strategy for backup. Do consider risks beyond just local computer hardware failures.

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