I have a several-year-old 6 TB Time Machine backup. I bought a new 12 TB drive, same manufacturer, which I hope to use to replace the old drive, but still keeping my old backups from the old drive (and now having room for more).

I understand Apple's guidance is "copy old-drive-content to new-drive-content through the Finder" and there is no other guidance.

My concern is this takes an inordinately long time. Like, two months of "Preparing to copy" with a slowly growing file count until this morning, evidently my machine had a system error and rebooted itself. So I'll be starting over. In the first day of the copy, the number of files being prepared to copy made it up to about 20M files. Then the rate of increase of that number decreased significantly. In the next two months, it grew to 30M total. I don't know how many files are on the disk (I didn't think it was prudent to compute this while the copy was progressing).

The concerns I have are:

  • Why does it take two months+ to "prepare to copy"?
  • Is there any way to speed this up?
  • Would any sort of command-line copy command be faster (in particular, not have to spend months preparing to copy)?
  • Is there any way to do this incrementally, e.g., prime the new backup disk with a recent backup then gradually over the next few months copy over older backups?
  • 1
    Use Disk Utility to "Restore" the old disk onto the new one. (Click Restore with the new disk selected, and then choose the old disk as the source.)
    – benwiggy
    Sep 18, 2022 at 20:59
  • I'll give that a whirl! Thank you @benwiggy.
    – jowens
    Sep 18, 2022 at 21:07


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