time machine backup fails, "create or skip"

Question

time machine backup fails, "create or skip"

I have two MBPs, one running Catalina, the other Mojave. I backup to an early generation Time Capsule, as well as a Synology NAS device. In the past 48 hrs, my backups on both devices started to fail, asking the question whether to create a new backup, or skip the backup (suggesting a corrupted backup file). After selecting "create", and after it comes "close" to completing the backup of approx 250gb, the backup fails. I then try to backup to the alternative backup device, to have a repeat failure, and posed the question to "create or skip." Between my two MBP's, I've tried 6 or 8 backups, and have yet to complete successfully. At first I assumed my early generation Time Capsule might be nearing end of life, but when I discovered the same error occurred on my NAS, I turned the source MBP. I've run FirstAid using the Disk Utility against MBPs SDD, which found no errors.

Given that I'm getting the same error on two MBP's, running two different OS, and attempting to backup to two independent backup devices, I'm lost.

Any ideas?

MacBook Pro 13″, macOS 10.15

Posted on Jun 26, 2020 5:23 PM

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Answer 1

Barney-15E

Level 10

116,710 points

Jun 27, 2020 5:36 AM in response to zman of Illinois

Perhaps it is something in the networking. Cables, protocols, router--that's where the two are similar. However, I'm not sure what would suddenly cause the problem.

The Time Capsule should probably be using AFP, but I don't know if it is capable of using SMB. The NAS must be using SMB.

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Answer 2

Barney-15E

Level 10

116,710 points

Jun 27, 2020 8:41 AM in response to zman of Illinois

SMB is enabled on the NAS.

Ok, but is that how Time Machine connects to it? If AFP is also available, then it might be connecting over that protocol.

Do you know if the NAS supports Time Machine over SMB specification? I think it needs to be using Samba 4.8 or later to support that specification. If it uses some other SMB/CIFS server, then you would have to ask the NAS manufacturer whether it actually supports that specification. Note that connecting via SMB is not the same as the server supporting the Time Machine over SMB specification.

Any NAS that suggests you use AFP will tend to fail as you describe because the version of AFP they use is a hack that doesn't fully support Time Machine. Apple never licensed AFP, so they are using a hack to make it work.

But, as you stated, it is odd that both the Time Capsule and the NAS is having the same problem. That's why I think it is something in the router or other networking issue. Are you using the Time Capsule as the router or is it in bridge mode with another router doing the routing?

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Answer 3

Old Toad

Level 10

210,597 points

Jun 27, 2020 2:05 PM in response to zman of Illinois

Try running Disk Utility's First Aid on the Time Machine drive. Be aware that it will take much longer due to TM's complex ecosystem of file permissions and hard links. So patience is a virtue and a must.

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