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User profile for user: 2pods2
2pods2 Author
User level: Level 1
16 points

Time Machine tells me disk is not available

Although Time Machine backs up my files on a daily basis, However it stops and gives me the following message everytime it gets to 261gb on disk or 73 backups, whichever happens first.


"Time Machine couldn't complete the backup, as the disk is not available@


Said disk is a external WD 3tb usb3 disk with plenty of space left, is solely devoted to Time Machine, was formatted on my M2 Max Studio.

I've run diagnostics on it, and it reports as OK, I've tried it in every usb/thunderbolt port on the machine, also in a usb 3 hub. It's installed OK, as I can see the backups.

It's formatted as a one big partition of 2.8tb quota.


Twice, I've reformatted it, started again, and it runs perfectly.....until it hits one of the two points above.

I'm mystified.

I'm running Sonoma 14.5

Mac Studio

Posted on Jun 14, 2024 8:29 AM

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User profile for user: Grant Bennet-Alder
Grant Bennet-Alder
User level: Level 10
133,351 points

Posted on Jul 12, 2024 9:50 AM

it is possible that your drive could be encountering Bad Blocks. The free trial of DriveDx could tell you that.


You check it error counters for 'Pending sectors'. That confusing term is the count of blocks suspected BAD, but as yet un-repaired (by substituting a known-good spare block).

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User profile for user: Grant Bennet-Alder
Grant Bennet-Alder
User level: Level 10
133,351 points

Jun 17, 2024 10:39 AM in response to Grant Bennet-Alder

So this is an Existing Time machine backup drive, directly connected to your Mac (not a network drive) with multiple completed backups and a partial backup already on board.


Solving this may take digging in the Logs to find more detailed error messages that have more information, or asking Apple support to help you read those log files.


to attempt this yourself, the tool to do this is Console.app

the item you likely want to examine is Diagnostic Reports

the filter/search you want to apply is backup


the most frequently found item is a micro-stackshot, which is not especially helpful. But if you find an error message that is recent, it may have more information with it.




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User profile for user: 2pods2
2pods2 Author
User level: Level 1
16 points

Jul 30, 2024 2:59 AM in response to 2pods2

I think I've finally cracked it.


After turning Time Machine off for a while, then re-selecting the same disk, but this time setting Time Machine to backup automatically, all is now good and has been for a while (I hope I haven't jinxed it, though).


I can even use it manually if I want it backed up before it's due.

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User profile for user: Grant Bennet-Alder
Grant Bennet-Alder
User level: Level 10
133,351 points

Jun 14, 2024 3:02 PM in response to 2pods2

use the Finder to see if the disk has become available again. If it has, tell time machine to "back up now".


when a disk becomes unavailable, one possibility is a corrupted Directory. Open Disk Utility, choose "show all devices" from the tiny View menu, and Repair in order:

the physical device, and

the container, and

the MacOS Volume.



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Time Machine tells me disk is not available

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