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Soba

macrumors 6502
Original poster
May 28, 2003
450
700
Rochester, NY
Edit: Found the problem after a lot of testing! See this thread for details and the fix.

I am running High Sierra 10.13.6 on my Mac Pro 5,1. A while ago, I replaced the Time Machine drive mounted in SATA Bay 4 with a larger drive. I cloned the old drive to the new drive using SuperDuper! to preserve my backup history and then retired the old drive. Backups are running fine.

In past versions of macOS (starting with Mac OS X Lion), a recovery partition was created silently on Time Machine drives upon completion of the first successful backup. I noticed recently that the recovery partition that allows booting directly from the Time Machine drive was missing. No boot option for the Time Machine drive shows in the Startup Manager (holding Option at boot time) and running `diskutil list` in Terminal shows only an EFI partition and the Time Machine data partition. I assumed this was because I used SuperDuper! to clone to the new drive, which would have cloned only the backup data partition, but in any case, it's possible my prior Time Machine disk did not have the recovery partition, either; I have replaced the Time Machine drive many times over the years and cannot recall when I last saw it appear in Startup Manager.

Assuming this is still supported, I would like the option of booting from the Time Machine drive in case of a disaster, so I removed the existing Time Machine backup drive from Time Machine preferences and unmounted the drive. I then erased another new drive connected via one of the USB2 ports, and as expected, macOS prompted me to use the new drive for Time Machine backups. I then let the first backup run to completion and macOS displayed the expected message saying the first backup was successful. I intended to then clone the entire drive using Carbon Copy Cloner to preserve the recovery partition.

But no recovery partition was created on the new drive. I tried the same procedure and re-wiped the new Time Machine drive on my Macbook Air 4,2 (also running 10.13.6) and got the same result. The Mac Pro and the Macbook Air have a few folders excluded from the backup, but these are folders such as my Downloads folder and large Fusion VM files, so I would not expect this to have any effect.

Perhaps I'm wrong in assuming that there should be a recovery partition on Time Machine drives, as there used to be. Are recovery partitions no longer created on Time Machine drives in current versions of macOS? Or is this happening because of a quirk of my hardware, or even a bug in 10.13.6, perhaps?

I'm happy to provide more details of my hardware, if needed. I don't use a sig because I own many Macs.

Thanks for reading.
 
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