What causes TimeMachine backups to fail on NAS devices?

I've been using Time Machine to a QNAP NAS for years and once I upgraded to 15.0.1, it stopped working. I even wiped the backups from the NAS and set it up from scratch, but it won't even start the first backup. Disabling the Mac firewall does not resolve the problem.

This isn't just NAS's. I have two Mac Mini's and an MacBook Air. The Air is a M2 running 15.0.1 on of the Mini's is a M2 running 15.0. The third Mini is the target and it is older. It is an i7 running 10.15.7. All it does is act as the target and has worked for years until this update. The 15.0 machine works fine the 15.0.1 machine, no dice. I have gone as far as completely reformatting the target drive and reconnecting the Air to it. The connection is initially made and the sparse bundle is created but then the backup goes into the abyss and I get a failure that says the remote disk disconnected.

I am yet to look into the firewall fix that people have been talking about but this as someone said is a complete dumpster fire. Apple has really dropped the ball with 15.0.1. That 15.0 machine isn't getting the update anytime soon.

It’s not NAS specific. It’s actually a network communications problem when the internal or even third party firewall is enabled. For me it’s the MacOS internal firewall but I’ve been reading others have a problem with third party.

To be clear, this is a problem with non-Apple firewalls, introduced by new code in 15.0.1. 

It’s not specific to a particular target system for a time machine network backup. 

It doesn’t matter what your target system is, or what your third-party firewall is. If you put 15.0.1 onto a machine that backs up to a target elsewhere on your network, then there is a very high likelihood that it will fail. 

If you turn off the firewall (or open specific ports) there is a very high likelihood that it will work again. 

There is a very high likelihood* that this has been caused by inadequate pre-release testing of 15.0.1. 

If you want to make the strength of your feelings known to Apple, do it here:

Feedback - macOS - Apple

*¿am I repeating myself?

I found a solution for me and Time Machine backups are now working. I had to remove my Time Machine target in the System Settings and had to reset the broadcast setting on the NAS:

After that Time Machine found the Time Machine target again and I could re-attach to the backup and continue. Now Time Machine works again.

I use corporate MacBook and cannot change FW settings because it is managed by the company.

Need a fix ASAP!

Hi

What worked for me is to set the Synology configuration as described here https://kb.synology.com/en-global/DSM/tutorial/Time_Machine_backup_failed.

On macOS system preferences I activated Windows file sharing. Now Time Machine Backup works fine.

I was having the same problems – TM backups to my Synology NAS failing midway (via samba and afps). I did as people suggested and disabled Lulu and macOS built-in firewall and the backup functionality did work, but I kept testing. I found that after permitting smbd AND Lulu as a process/application in the firewall settings, I was able then able to enable the firewall AND Lulu AND successfully perform a TM backup. I'll see how it stands over time, but I wanted to share in case others would like to try this solution and report back if it works for them, too.

On a separate issue, TM backups tend to fail if you lock the screen. Presumably, Apple's security autocrats decided this was dereliction of duty. The commandants insist we remain handcuffed to us computers during backups. Of course, anyone with an iota of understanding of human nature knows that people will do what is easiest – leave their computers unlocked and insecure. Self-defeating!

To the person (kolorfilm) whose post just got deleted for mentioning the “B” word.

No it doesn’t fix it.

Adrian.

I have never used a NAS but the experts that are far more knowledgeable than myself would probably not recommend it. I read a article about TimeMachine yesterday and a question similar to yours was asked in the comments.

I can't even restore to prior time on my Time Machine to prior update. But it says it can't do it because it says the library files can't be modified or deleted because they are needed by mac. It's useless. 2023 expensive MacBook Pro that is now absolutely useless...can't even use both monitors unless I plug them in manually AFTER I turn my computer on.

Some success now!

After trying all of the above in my previous post, I was FIRST able to successfully complete a Time Machine backup to the external NAS (a WD 6TB hard drive) on the Airport Extreme. Not sure why it worked this time. But the backup to the M1 had failed again.

Finally, I tried one more setting change on the Mac Mini, in the energy saver section: I switched OFF the option to put hard disks to sleep when possible. Actually, the Mini has external SSDs, no external USB hard drives. Also, the switch for prevent sleep when display is off was switched OFF on the Mini.

This time the backup to the M1 Mini from the MacBook succeeded. Possibly noteworthy is that my MBP has about 750 GB used, and the .sparsebundle file on the Mini is just over 1 TB in size. I do have a Netgear Orbi A3000 mesh wi-fi network with 2 satellites (RBR50 and RBS50 x 2) with Backhaul enabled over which the Time Machine backups occur.

While I'm glad the backups have completed, I'm not really sure if any of the changes I made really helped.

Well, here's the deal:

15.0.1 made some changes and it relies on your firewall to protect you - your provider should have updated the files after the release of 15.0.1. After spending much time with a smart guy at Apple Support, we solved the problem by updating my firewall software (Sophos) and, lo and behold, the backup now works. For me, it was that simple (the hard part was getting it figured out!) Give it a try and holler back...

To be clear, it is not the apple OS firewall that was the problem for me. it was the external firewall (mcAfee, Sophos, etc). For me, I updated my Sophos firewall to the latest version and the problem went away. Sophos had a blurb about this on their support site. try updating your external firewall (not the definitions but the actual program) and see if that fixes it for you. I am now using 15.0.1 TimeMachine with no issues. Have done 5 backups perfectly.