Time Machine performed a validation & needs to start over

Time Machine just went to do a back up and bounced up the message:

Time Machine completed a verification of your backups on “WDMyCloudMirror.local”. To improve reliability, Time Machine must create a new backup for you.

Click Start New Backup to create a new backup. This will remove your existing backup history. This could take several hours.

Click Back Up Later to be reminded tomorrow. Time Machine won’t perform backups during this time.

I gather that “To improve reliability…” is code for “your backup is completely stuffed”…

TimeMachine is (was) backing up a MacBook Pro to a NAS of which 1TB had been allocated to TM and still had about 490GB free. (So it’s not an out of space issue, and if it was doesn’t it remove earlier version and keep a ‘rolling backup’?).

The entire NAS is backed up periodically to a couple of external USB disks so I do have older copies of the Time Machine files.

Does anyone know how TM keeps track of where it’s up to? Is the “index” / control config stored on the the Mac or within the sparse bundle? My thought was, can I copy the older backup off the USB onto the NAS and set it going again (thus retaining my TM history) or will that result in a mismatch between the backup files & where TM thinks it’s up to, thereby completely confusing it?

Thanks in Advance…!

That’s my take on it. I’ve found Time Machine nice when it works (and really dazzles Windows-using friends!) but fairly unreliable, so it’s just one of several backup approaches I use.

It uses some file system extension capabilities in order to work. You should be able to move the sparse images around but any attempt to mess with the innards will tend to lead to disaster.

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Thanks, I might give it a whirl though it’s going to have to wait till the weekend, hopefully there’s no way I can make it any worse than it already is! And I’m definitely not brave enough to start tampering with the innards! :wink:

In case it helps, some of us found that Mojave messed up our TM, causing this to happen on loop. If that happens to you, download Mojave again and reinstall it to fix it.

I would definitely recommend not doing that, as it seems destined to bring sorrow upon your household.

However, if you are in the “nothing to lose” mindset, then the tool you need is in Terminal.app. Run man tmutil and read from there.

You can tell Time Machine to forget its destination and then adopt the older one. I don’t remember the exact syntax (on my iPhone atm) but the man page should get you started.

If you can afford do do so, pick up a new drive for your new TM backup. Put the old one in a drawer and, once you are confident with the new TM backup use the old drive (suitably reformatted and checked for bad sectors) as a carbon copy clone (or similar mirroring software).

Of course, if you have already done the above, you would have an older drive you could use this time :slight_smile:

@GraemeS, Thank you for that link, I’d not initially twigged on to that probably being related as it had been ticking away quite happily for some time (I’d figured if that was it then it’d have gone boom sooner). Having reading that thread a bit more attentively it seems like a strong candidate. A re-install is as about as appealing as toothache though :frowning:

@tjluoma, thanks for the info, I’ll have a read up on tmutil, sounds like the sort of thing I could cause some trouble with. I’ll see how brave I’m feeling this weekend :smiley:

thanks @Philrob, funnily enough I’d already been toying with the idea of getting another drive & kicking off a 2nd / separate Time Machine backup before this one blew up. Might be a good time to dive in on that. :slight_smile:

@SpivR, thanks, I think after this I’ll be completely re-working how I do backups. I had been very pleased with TM given (as you point out) the set-it-and-forget-it nature, flaky is just not a feature you really want in a back-up tool though. :wink:
Bomb-proof… Bomb-proof is what we’re all looking for in a backup tool. :smiley: