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macrumors 6502
Original poster
Sep 29, 2009
Is it okay to use APFS in these situations? These drives don't have OS installed.

1. External SSD with Time Machine
2. External SSD without Time Machine
3. External SSD Encrypted with Time Machine
4. External SSD Encrypted without Time Machine

5. External HDD with Time Machine
6. External HDD without Time Machine
7. External HDD Encrypted with Time Machine
8. External HDD Encrypted without Time Machine


macrumors 6502a
Apr 10, 2015
Cheshire, UK
Time machine won't work on APFS

I made the mistake of converting mine to APFS and this is what I got so I had to re partition it back as there is no conversion the other way.
Screenshot 2018-09-29 at 11.31.01.png

The other non Time Machine options are probably OK but it does warn you that you can't use it with earlier OS versions.

I seriously suggest verifying the drive before doing a file system conversion too as mine converted but the superblock was so corrupt it wouldn't repair so I ended up reformatting it to APFS and then I got this message.
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macrumors 68040
Apr 26, 2017
Another reason to wait with Mojave upgrade.
Why have hurry?
Not, when Apple themselves haven’t made it possibly to backup within their own system.
For sure, I use CCC too. But anyway...

Thanks for the info.


macrumors 6502a
May 23, 2008
So i am confused...i have an iMac with a fusion drive that is running MacOS Sierra. I am just about to upgrade it to Mohave. However, will my Time Machine backups be messed up afterwards? I was going to upgrade my iMac with my Time Machine backup unplugged just to be on the safe side.


Sep 3, 2006
No it won't mess your Time Machine backups. The only way to mess it's if you mess with it yourself.
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