Encrypted drive does not work with time machine?

[stanw]

I formatted a 6tb external drive with disk utility with encryption. After, I selected to use it with time machine, though it prompts me to decrypt it with my password and then it gives me an error. I reformatted and went through this process 3 times with the same result. Is this a high sierra bug?

Thanks.

 

[stanw]

Anyone on this?

Thanks.

 

[treekram]

If you formatted the disk as APFS, at present you can't use it as a Time Machine disk.
https://support.apple.com/guide/mac-help/disks-you-can-use-with-time-machine-mh15139/mac

With an external HFS+ encrypted disk used for TM, you plug it in, the system asks for the password to decrypt the disk and then when TM does it's next backup, it shouldn't ask for the password again. If you're using HFS+, post the error message you get.

 

[stanw]

It was the journaled encrypted option

 

[treekram]

It was the journaled encrypted option

So that says you're using HFS+ on your backup disk. But you need to explain the sequence (when these happen in relationship to each other) of:
1) when you attach your external disk
2) when the prompt for the password comes up
3) when you start your backup
4) when the error message comes up

You also need to post the error message. The error message is really a very key piece of information.

I can do a Time Machine backup of my High Sierra 2012 Mini to an encrypted external HFS+ USB disk without a problem so it's not by design that you're having a problem - something is different in your situation that is causing the problem.