My external drive does not show up in Time Machine

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Level 1

11 points

My external drive does not show up in Time Machine

I use Time Machine with an external NAS with no apparent issues. I have an external drive that I want to back up to Time Machine when it's connected to my laptop. I have no excluded directories in my config, and the "estimated backup size" is the total of my laptop's internal drive plus the external drive. So far so good.

However when I enter Time Machine and go back in time a bit, the external drive (while plugged in) is greyed out. The external drive is not always connected, but I waited for a couple of backups to complete before trying this.

What's the problem?

Thanks!

MacBook Pro (2020 and later)

Posted on Feb 26, 2022 11:37 AM

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Answer 1

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tribu176 Author

Level 1

11 points

Feb 27, 2022 11:57 AM in response to Tesserax

I found the issue. There was a weird problem with the cable that connects the external hard drive. The drive would appear when plugged in, and the overall usage of the disk was reported correctly, but the content (which is a 100GB Photos archive) was reported as having a size of zero.

Swapped the cable, disk worked normally and Time Machine happily backed it up on the NAS. Conclusion: always check layer 1...

Sorry for the noise :)

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Answer 2

Tesserax

Level 10

149,069 points

Feb 26, 2022 11:53 AM in response to tribu176

Is this external drive, formatted in APFS, HFS+, or something else? As you know, using an external drive on occasion for Time Machine is not a very efficient method for these backups. That's where your NAS would perform better.

Regardless. when TM runs it creates local snapshots that are stored on your notebook, until the external drive can be re-attached. The reason I asked about this drive's formatting is how TM stores those backups on that drive.

Ref: Time Machine to APFS: Understanding backups - The Eclectic Light Company

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Answer 3

tribu176 Author

Level 1

11 points

Feb 26, 2022 12:35 PM in response to Tesserax

Hey Tesserax,

Just to clarify: I'm not using the external drive for time machine but I want to back it up on Time Machine via the laptop. I'm happy with the NAS as the overall backup destination, as you mentioned :)

The external drive is in Mac OS Extended Journaled format btw.

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Answer 4

Tesserax

Level 10

149,069 points

Feb 26, 2022 6:12 PM in response to tribu176

Ok, well in theory, TM will automatically back up your device's system drive AND any directly attached external drives. You shouldn't have to designate the external drive for this to happen ... if you attach this external drive to your notebook, and then, start a manual TM backup, does the back up include both devices to your NAS?

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Answer 5

Tesserax

Level 10

149,069 points

Feb 26, 2022 1:55 PM in response to tribu176

Ok, just to be sure I understand, you want to back up, using Time Machine, BOTH your notebook, AND an external hard drive attached to it, to your NAS ... correct?

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