What causes TimeMachine backups to fail on NAS devices?

Just spent an hour+ with apple support. had me boot into safe mode, shut down my firewall and the backup worked! Obviously still an issue but at least I got a backup to my NAS. after it's finished I will reinstall the operating system, turn the firewall on and try again. stay tuned...

After two failed migrations on 15.0.1 (I thought that it was my fault the first time …) I reverted the MBA M3 to Sonoma 14.7, and migrated again. TM works now, and I’ve created a usable sparse bundle from the new machine (as well as having two good ones in reserve from the old machine.

There are better ways to spend a weekend.

I have spoken to my firewall provider, and understand that 15.1 fixes the various firewall and network problems that were so freely given in 15.0.1. Lets hope that it’s soon and that they’re correct!  

I have the same setup on 4 x machines and it 15.1 is working fine, 3 x MacBook Pros and 1 x MacBook Air.

Little Snitch 6.1.2

I guess you could uninstall Little Snitch to check if it is that getting in the way?

Adrian.

I have the same NAS setup. My Time Machine backups (scheduled and manually invoked) have failed with the installation of the Sequoia 15.1.1 update, for a variety of reasons - eg: network connection dropped. They might progress a few MB, then fail. Was working perfectly before then, and there's not been any other changes to my NAS or network.

I have tried all of the above suggestions, and much more, but no go.

Whatever the security issue the update "fixed" was clearly some serious sh1t that it's broken other things in the process. I just wish they'd explain what it was they did - but I guess that'd help the bad guys...Meanwhile, hoping Mac's hard drive doesn't die anytime soon!

I have just updated three machines to 15.1.1 (avoided 15.1).

One is a mac mini 2018 intel, which has two LaCie drives attached for network time machine backup, the others are both MBA Mx laptops.

One of the MBAs was on 15.0.0 while the others were on 14.7.0. In that situation, I had various and many failures with the networked disks disappearing during a backup of the 15.0.0 machine. Also repeated failures of screen sharing to the mac mini.

With all machines on 15.1.1, those problems have stopped. I have run several backups from both laptops to the mini and screen sharing between all three works fine.

This has been a very unsatisfactory series of events, and I'm sure that it hasn't entirely gone away, especially as some NAS users are still having problems.

In conversation with an Apple person, I asked why they didn't have field testers (you or me) who could run through the non-standard setups that are likely to occur in abundance outside Cupertino. The response was that if I encounterd a failure, I could mail the logs, but there was no plan to introduce field testing of that kind. In the dim and distant, I worked on IBM MVS/370 -- IBM's standard policy seemed to be to ship buggy software, then let the users fix it and send the patches back to base for distribution round the world. It wasn't ideal, but it worked.

Apple, perhaps you could give it a thought. The Beta programme obviously didn't pick up this mess.

I've had the same problem too. Time Machine backups started to fail after upgrade to OS 15.0.1. Both on a network attached storage (NAS) device AND on a Mac Mini as backup destination.

On the Mac to be backed up (MacBook Pro M3, source), I went to Settings, then Time Machine, and removed the destination that was failing. But I could not add it again until I did the following.

Backup disks you can use with Time Machine - Apple Support

For backing up that Mac (source) to another Mac computer (destination): I went to Settings on the destination Mac, selected General, File sharing, added the destination device/folder, and then right clicked on the added device/folder, and selected “Share as a Time Machine backup destination,” then clicked OK.

Then on the Mac I wanted to backup from (source), I saw the external Mac destination for doing the backup. Add the new destination, choose to use the same backup device/folder as before, and let it do the next backup.

However, it failed again on the Mini as destination: "The network disk disconnected from your Mac while backing up".

The NAS I'm using is on an AirPort Extreme (old Apple device with USB connection to a 6TB hard drive). It very recently started failing backups too with the same error message as for the Mini as a destination.

Finally, I am running Bitdefender on both the M3 MacBook Pro and M1 Mini, BUT I have disabled its protection for Time Machine backups since that previously interfered with doing backups over the LAN (several years ago now).

I have not disabled the MacOS firewall in network settings on either the MBP or Mini.

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 spoke Apple support today. I got a senior advisor who escalated it to engineering. Engineering decided that it was my problem and I should call Synology. I don't believe that it's Synology's problem based on what I've read here. But unless others call they will pretend it's someone else's fault. The senior advisor was very pleasant and helpful. He says the engineering team counts the number of problem reports and will act if enough people complain.

It might be helpful if people would contact Apple support: https://getsupport.apple.com/solutions/call. The wait time was not long when I called. If you call make sure you get to a senior advisor who can escalate. They will take some data from your machine so do this when you have some time and are near your Mac and backup server.

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!

+1

Temporarily disabling the firewall and initiating the backup manually seems to be the only reliable workaround.

Fixed in 15.1 (at least on my system) with the Firewall on. Yay!

Fixed in 15.1

Issue is fixed on 15.1, backups from TimeMachine now copy to NAS without any alterations to the settings from 14.7.