What causes TimeMachine backups to fail on NAS devices?

Even though AFP is not listed as a way to connect to a NAS drive for Time Machine, I did exactly that--turned on AFP on my Synology DS218J NAS, connected to the server via AFP, and *I think* I selected the AFP-connected drive designated in the Synology settings for the Time Machine backups, and so far I'm 10%/10 GB into the initial backup with the firewall turned on.

I'll have to do some more experimentation, but connecting via AFP may be a workaround.

At least I think I'm using AFP...I turned it on in the DS2J settings, then when connecting to an external server I typed in "afp://ds218j.local:5000" and it connected to all the shares on the DS218J. I set up Time Machine to the "Time Machine Backups" share, firewall on, and the backup is progressing...14%/28GB, five hours to go over wifi.

I may try turning off SMB on the DS218J (after the other Macs in the family do their backups) and see if it still works on my 15.0.1 MBA.

Mine stuck at "connecting to backup disk..." and the log just said "Bonjour resolution not possible for 'afp://backupworker@x.x.x.x" indefinitely. Apparently I'm able to mount the AFP volume in Finder or `mount_afp` and I can tell Bonjour broadcasting works just fine, but the Time Machine just can't.

Im having a similar issue. We use a Synology Nas to edit footage from. Its been fine for near on 2 years. I updated (mistake) 2 weeks ago and then all of a sudden monday monring the server is disconnecting whenever it needs to do something ie: Exporting a video, reading the timeline, importing photos. It doesnt seem to matter about the file size. It just disconnects. Any ideas here? its only an issue with the NAS. Other drives like the Black Magic Cloud unit is fine. Also transfer speeds have slow right down

I have the same setup as you. I had to reboot twice after the 15.1 update and I started a new backup (because I thought that the old one might be corrupted). I don't know if the new backup was required but the reboots certainly were. Everything seems to be working well now. Good Luck!

I did this already with 15.0 + 15.0.1 and that fixes it also temporary, but I came back after a while. Will try this as well with 15.1 but this shouldn't be the solution to remove the whole backup and start again.

Disabling the firewall worked for me. I think I recall it working once or twice without deactivating the firewall on 15.0.1.

Now after updating to 15.1, it seems to work reliably.

This is also backup to a Synology NAS.

summary: 15.1 fixes it for me.

15.0.0 and 15.0.1 broke Time Machine backups for me as described in this thread. disabling Apple firewall in network settings was the workaround.

15.1 fixes it. I no longer need to disable the Apple firewall for Time Machine backups to complete on my Symplogy NAS.

Software: Little Snitch Mini and Cloudflare Warp.

hardware: MacBook Air M3 and Synology DS220+ NAS.

So I can back up with Time Machine now I am on Os 15.1. But only triggering the back up manually. If it's on the normal hourly auto. setting, it looks fine but then reverts to the "server disconnected during the procedure" type error log. But at least I can now back up. Definitely not moving from Os14 for other devices.

That because it Disney at every Mac Upgrade each year! That’s why I consider Time Machine to to basic and myself went shareware backups that continue programs instead where it picks up older backup files!

Appears fixed in Sequoia 15.1 (definitely broken in 15.0.1). I am now able to turn my mac's firewall back on. There was also an update to Synology DSM 7.2.2-72806 I installed at about the same time. So between the two updates, it is now fixed.

Not to beat a different dead horse but there is another major problem introduced with OS 15: typing lag with long entries in Messages and in Notes. Also OS 15 has not fixed the perennial problem with Messages not updating. This second problem has been around since OS 14. My workaround is turning off and then turning back on wifi which is what I did each morning and now still have to do with OS 15 and now under OS 15 I have to do it several times a day. I am convinced they are 100% aware of these problems but either have no solution or more likely just not motivated in fixing them.

I have already reported to them twice that it is happening also with Time Machine with both NAS and USB connected hard drives. I do not know what do they need to convince themselves that this is on THEIR end and not the users. The update to 15.0.1 broke it for me when TM was working fine with both methods.

Turning off the Apple OS firewall is not an elegant workaround that they should be proud about.

When my display is asleep and Time Machine attempts to run, it fails and presents the error message "Time Machine couldn't back up...". Waking up the display and manually selecting a backup results in success.

This bug has been reported for months in various other forums.

Yet another Sequoia bug. C'mon Apple, get this fixed and do better with your QC in advance of new OS releases.

When this thread got started, I also noticed in the popular press that Synology NAS devices were vulnerable to remote attackers. See the latest update: https://www.synology.com/en-global/security/advisory/Synology_SA_24_27 . I don't use Synology NAS, but just making the observation.

In my case, I'm doing backups in my home wi-fi LAN, and I'm doing backups from one Apple device (MacBook Pro (Mac15,7) [Source is Mac SSD internal] to 2 different destinations: 1) WD hard drive attached to an old Airport Extreme via USB-A, and 2) Mac Mini (Mac16,10) with a Samsung T7 SSD connected via USB-C. My source drive contains about 770 GB of files to be backed up via wi-fi network.

Like many others in this thread, my Time Machine (TM) backups started failing after upgrading to MacOS 15.0. The reasons for failure were sometimes due to a network disconnect by my MBP or to the remote destination device not cooperating with TM.

I've had problems of TM backups failing after OS upgrades a number of times in the past 12 years with Apple products. Generally speaking, I've had the best success by creating a new backup (after first moving the old backup destination files to a different device, so I could restore from it if necessary). The new backup can take days to complete, so I do what is needed to speed that up (since failures would often happen after many hours had expired).

After the first full backup was successfully completed, then I changed my Lock Screen settings back to what I normally prefer (on both source and destination).

Most recently I changed Lock Screen settings while keeping the MBP connected to power with lid open, so it wouldn't go to sleep during the TM backup. Likewise for the destination machine (Mini) and its external drive. I manually started the backup, which took about 22 hours for about 750 GB, not letting either the source or destination sleep.

Also, it seems that, over the years, MacOS has changed some of the instructions for TM, depending on the OS version, especially in how to prepare the destination. I have found it worthwhile to read the Apple Support docs for the current OS version, and checking all of the various settings (e.g., especially for file sharing on the destination and settings for folders for TM backups).

Sometimes my antivirus software has interfered (BitDefender) and I have set my Time Machine protection to Off.

I have not changed MacOS firewall settings on either source or destination. I keep the firewalls on.

Yeah, this is annoying and takes time to debug. There's lots of places where problems can occur, and that's what makes it so perplexing and frustrating at times. I also use other backup strategies besides TM for really important files, using external cloud services for those.