Time Machine error - "two disks have the same name"

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Time Machine error - "two disks have the same name"

I'm now repeatedly getting a "Backup Failed: Time Machine couldn't back up to "Time Capsule"" error when trying to run Time Machine. The detail of the error is "Two of the disks to back up have the same name. Rename one of the disks named "Macintosh HD".

However, I only have one visible disk partition named Macintosh HD, as shown by either Disk Utilities or by using diskutil list in Terminal.

Other users who've reported a similar problem relate it to having carried out dual or more install of Catalina & so ending up with multiple partitions with the same name. However, that's not the case here - relatively new iMac which has been updating using Software Update & had no manual updates at all. So does anyone have any ideas as to what's happening here & what solution(s) there might be?

Many thanks in advance for any help.

iMac 21.5", macOS 10.15

Posted on Feb 19, 2020 1:16 PM

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Answer 1

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Kappy

Level 10

361,843 points

Feb 20, 2020 8:21 PM in response to paulwade

I see nothing wrong with either the internal HDD+SSD nor the external Time Capsule. It all looks normal. The error is from the Time Capsule, so the first thing to look at is the Time Machine preferences and see if the configuration is OK. If it is, then it may be you will need to erase the Time Capsule drive before doing a Catalina backup.

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Answer 2

Kappy

Level 10

361,843 points

Feb 20, 2020 12:13 PM in response to paulwade

What is the Time Machine backup drive? Is that Time Capsule? What is the "plain HD 'partition'?" Your iMac has a HDD and a PCIe SSD joined together as a Fusion Drive? If so, then you should consider how the Fusion Drive is formatted. It would appear it is formatted APFS, but it should be formatted Mac OS Extended, (Journaled) for better performance. This is also the way the Time Capsule's drive should be formatted.

I'm not really getting the picture of how all the drives are formatted and configured. So, would you take a screen snap of a directory listing in the Terminal? Open the Terminal and enter this command line: diskutil list. Press RETURN. You can change the Terminal window's size so that the entire result can be seen. Now, take a snap of the window:

How to take a screenshot on your Mac

Capture, Save or Record Screenshots in Mac OS X - Help Desk Geek

OS X Screen Capture Shortcuts

(⌘⬆︎3) Command-Shift-3 Capture the screen to a file

(⌘⬆︎⌃3) Command-Shift-Control-3 Capture the screen to the Clipboard

(⌘⬆︎4) Command-Shift-4 Capture a selection to a file

(⌘⬆︎⌃4) Command-Shift-Control-4 Capture a selection to the Clipboard

(⌘⬆︎5) Command-Shift-5 Invoke new screen grabber

I suggest using either (⌘⬆︎4) Command-Shift-4 or (⌘⬆︎5) Command-Shift-5. Both enable you to select a portion of the screen. Select the Terminal window containing the result of the diskutil command. Then use the image upload icon in this message editor's toolbar. It's the right-most icon next to the black button.

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Answer 3

Kappy

Level 10

361,843 points

Feb 19, 2020 1:34 PM in response to paulwade

Open Disk Utility and see what is displayed. Be sure to click on the View menu in the upper-left side of the toolbar and select Show all Devices.

Note that Catalina now creates two volumes within a single "container" on an APFS formatted drive. Does your computer have a HDD or an SSD? The latter would be formatted using APFS but not the former nor a Time Machine backup drive.

The two volumes would, for example appear as: Macintosh HD and Macintosh HD - Data.

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Answer 4

paulwade Author

Level 1

40 points

Feb 20, 2020 2:58 AM in response to Kappy

Hi Kappy,

Thanks for the reply.

Ihad checked using Disk Utility & it shows my internal drive as a "Fusion Drive", within this "Container disk2" & within that "Macintosh HD" and "Macintosh HD - Data". The plain HD "partition" has the Mac smiley face startup icon, and the "HD - Data" partition has a House icon.

Current sizes of both are as follows (if this helps):

HD: Used 11.05GB; Other Volumes 347.65GB; Free 668.84GB

HD - Data: Used 340.38GB; Other Volumes 18.33GB; Free 668.84GB

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Answer 5

paulwade Author

Level 1

40 points

Feb 21, 2020 4:52 AM in response to Kappy

Thanks Kappy,

I'd already tried that - I've checked the Time Machine preferences & couldn't find any obvious errors, so I reformatted the external Time Capsule disk & attempted to do a fresh back-up, but I continue to get the error message. Regarding your previous point about the formatting of my Fusion drive - this is how it came, out of the box; I've done nothing with it regarding formatting. My external disk called Time Capsule is formatted as you suggest - Mac OS Extended, (Journaled).

Any other ideas?

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Answer 6

paulwade Author

Level 1

40 points

Feb 20, 2020 3:14 PM in response to Kappy

The back-up drive is a 1TB external HD which, up until yesterday, was working perfectly with Time Machine,

Here is the output from diskutil list:

Thanks again for the help.

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Time Machine error - "two disks have the same name"

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