Time Machine Backup Not Mounting - Strange Errors

[mad cow disease]

I have an external HDD (encrypted) I've been using as a Time Machine backup. A couple weeks ago it stopped loading. I can see the drive in Disk Utility, but when I go to mount it -- the software tells me the volume can't be read, and gives me the option to either wipe or eject it. Running disk first aid on this drive tells me there is corruption it can't fix.

Loaded recovery drive, attempt to mount the drive, it asks for the password, accepts it, then says the drive cannot be mounted with the error com.apple.DiskManagement.disenter error, -119930868. Running Disk First Aid, similarly, doesn't do anything. The eval/repair fails.

The volume IS formatted as HFS+ (disk utility recognizes it as "corestorage volume"), but the AFPS conversion option in Disk Utility also fails. It's not the USB cable, I've had it plugged in directly, via a hub, neither of those makes any difference.

What are my options? I'd prefer not to wipe this if I have to, it's got 18 months' worth of backups. Thanks!

 

[TriciaMacMillan]

I know there are ways to repair an image, but let me tell you that the first thing you should do is to get another external drive to start backing up to. You may be able to repair the image, but you shouldn’t rely on the drive any more. In my experience, it’s not worth trying to repair and continuing to use a damaged Time Machine image, as usually, it will fail again after only a while.

That said, I’m sorry I don’t remember how to repair the image. I only remember that there were several ways, and some worked in one situation, while others worked in another, and they were all very time consuming.

 

[mad cow disease]

I followed you until you said "image." The volume appears to be intact, but is not mounting. It doesn't look like hard drive failure. Disk Utility recognizes that a volume is connected -- but will simply not allow me to do anything to it. The only thing I've done in the past two weeks is go from Mojave to Monterey.

So this doesn't really, to me, seem to be related to hardware. It sounds more like software.

 

[TriciaMacMillan]

Well, yes, „image“ is not really correct here. The image in this context is the logical organization on the hardware device, so rather it’s rather the file system. I make my backups to NAS drives, so I’m used to speak of images. Sorry for that!

I see why you think it’s not related to a hard error, because I have been thinking the same way in such situations, but in my experience, it always turned out to be a worn down device in the end.

 

[TriciaMacMillan]

As you speak of upgrading to Monterey, did the drive cease to mount at the same time?

I think I’ve read that Monterey (or even since Big Sur) doesn’t want to do Time Machine backups to HFS+ (or macOS Extended) any more, but only to APFS, but I’m not sure if that was really only about images.

However, that doesn’t explain why it doesn’t mount outside TM.