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I have a Time Machine backup on a USB ssd I would like to move the backup to a NAS. However, every article I have seen about moving Time Machine backups refer to Backups.backupdb file/folder. When I examine the contents of the backup there is no Backups.backupdb but just a number of Time Machine Backup files with the date and time e.g. 2021-10-14-143009. The backups all work and I am able to select a date and reinstall from them. So, am I able to just copy these files to a NAS or is the way Time Machine stores on a NAS different and why is there no Backups.backupdb file/folder?

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Your last question first! Why no Backups.backupdb?

Until the last 15 months, Time machine formatted the destination drive as HFS+ and placed each backup inside the Backups.backupdb folder. Each backup appears as a folder with all source folders and files inside it. It uses hard links to avoid really duplicating the files in each backup. The hard links (particularly those for folders) are the main cause of backup corruption.

Since Big Sur, new Time Machine backups format the destination as an APFS volume. Each backup appears as an APFS snapshot. Again all snapshots have all source folders and files. The magic of APFS avoids the duplication of files. This is a much more robust storage and in nearly every way is better.

Can you copy files to your NAS?

Yes, but not easily if you want to preserve all the backup history. My advice would be to copy one snapshot to a somewhere on your NAS. This will lose all your history, but will be simple to do. Of course, you don't need to that if you keep the SSD.

Advice

Assuming it does support Time Machine, start a new backup to the NAS.

Keep the SSD as it is until you are confident you will never want its content.

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  • Thank you for your comments and advice, that certainly makes sense. My NAS says it supports Time Machine but does not support APFS, does that mean the Time Machine backup may not be as robust?
    – Martin
    Dec 15, 2021 at 10:02
  • @Martin On the NAS, macOS will create a sparse bundle using whatever disk format is on the NAS. But the virtual disk inside the sparse bundle will be formatted as APFS and that is where TM will put the backup. From the APFS point of view just as robust as directly attached storage.
    – Gilby
    Dec 15, 2021 at 10:47
  • that's great, thank you so much for your help.
    – Martin
    Dec 15, 2021 at 12:43
  • What if the original external disk no longer exists (failed) and we wish to restore the data from the backup to a new external disk? How do we make Time Machine associate the backup for the failed disk with the new external disk and then use Time Machine to restore the data to the new external disk? I am trying to help a Big Sur user facing this situation. Though I have an idea, I am not 100% sure and I don't wish to make things worse. Can you pls take a look if you have not already done so?
    – Alper
    Jan 19, 2023 at 0:43
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    @Alper I have made an answer to the other question. Thanks for pointing it out.
    – Gilby
    Jan 19, 2023 at 3:58

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