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I have just upgraded my 2018 Mac Mini to MacOS 15 Sequoia.
Since 2019 it has always backed up to a folder called TMFolder on a Synology DS413j.
( My partner's Mini also backs up to the same NAS, but hers is still on Sonoma. Her backups still run successfully. )
Every time Time Machine on my Mini tries to backup to the NAS now, it reports:
The backup will fail anywhere between one and five minutes after starting.
Mac mini, macOS 15.0
In my case I had updated to 15.0.1 and then experienced the problem. Turning the macOS firewall OFF was the only way I've found to complete a backup to my Synology NAS. Previously I was able to back up with the firewall on while on Sequoia 15.0.
I am having EXACTLY the same problem with both my MacBookAir M2 and with my iMacM1, both on Sonoma, and either when they back up on the Synology NAS (DS218+, 7.2.2) or on an old Airport Time Capsule. This started after the Sonoma upgrade and seems to happen when the computers are inactive/sleeping. I have the impression the backup might start, but then it is aborted because the Mac goes to sleep and cuts off the connection. Files "unavailable" and backup tha will resume "when your Mac is unlocked" let me think about an issue on the mac/sonoma side.
Synology SMB Services beta didn't help me (with DS218+) - still "Backup couldn't be completed...", no matter whether via wifi or LAN. Time Machine on SSD connected via USB-C does however work.
If you can upgrade to macOS 15.1 on Monday (10/28) it will interesting to see if it resolves your issue.. It does seem to help with the Firewall problem.
Verified that the new macOS update fixed the issue.
Now I hope everyone is some what happy that Apple fixed a problem that never should have occurred.
Update 29th Oct: After updating to macOS 15.1, I'm able to backup to my NAS with Time Machine without issues (with Lulu and firewall enabled).
I upgraded my macbookair M2 to 15.1. It is not helping. I get the error "time machine did not finish backing up because some files were unavailable. Backups will resume when your mac is unlocked".
I am convinced there are two issues affectingTM backups: the first, linked to firewall etc. which appears to be solved by 15.1, the second has something to do with "sleep" or inactivity control. If the mac goes to sleep or is inactive during backup, the error shows up. No way out...
Admittedly, it may just be a huge coincidence. I went to Synology Support, and discovered that the version of software I'm running ( DSM 6.2 ) is end-of-life come October. My NAS can't update to a later version.
As it is 10 years old, I might just upgrade and build a new one.
When will Apple crushes this bug finally? In version 20? Djeezzz.
It’s not an Apple bug. It is a Synology bug.
Prior to their SMB 3 implementation, they use Netatalk which is a hack of Apple Filing Protocol (AFP). Apple has never licensed AFP. When Apple switched to SMB networking, they set a specification for Time Machine over SMB. It is up to Synology to support that specification.
Well, in my case, it's neither an Apple bug nor a Synology one.
I use some anti-malware/anti-intrusion apps from Objective-See Foundation. I disabled both BlockBlock and LuLu and the issue went away. I'll be sure to pass on this info to Objective-See !
I am running the final release of macOS 15 and fixed the issue by going to Apple > System Settings > Privacy & Security > Full Disk Access > toggle ON smbd. It seems macOS 15 disables the 'smbd' by default. The 'smbd' option provides filesharing and printing services using the SMB protocol which is what Synology is using to broadcast its file and folder shares.
I'm experiencing a similar issue. Time Machine backups occasionally fail, and file transfers to my NAS over SMB frequently cause my Macbook to disconnect from the NAS.
MacBook: Apple M3 Pro MacOS 15.0 (24A335)
NAS: DS918+ DSM 7.2.2-72806
Thank you for posting your experience. so you essentially re-did the macOS<>synology time machine integration and it's still not working the same as it was prior to the update from sonoma to sequoia? new folder, proper time machine folder settings, create the new time machine backup, etc... you did all that and it's still not working? ughhhhh
For me, that's always been the workaround that i've found solves these problems after a new macOS update. When macOS updates, can't think of a year that I wasn't forced to completely reintegrate time machine with my synology. it's always awful every year, but at least it still works in the end... not this time tho?
'Fraid so.
I've chatted with Apple twice now.
The first time they asked me to try and start the iMac Pro in Safe Mode (failed with same error); to create a new account (failed); and reinstalling Sequoia (initially seemed to work, but then it failed overnight with the same error and has failed every time since).
I've chatted with them again and I'm waiting for a call back. First line support is saying they've not heard of this error before, so I have pointed them to this thread.
My MBA is updating completely reliably throughout.
I'll keep people informed.
I am afraid the problem is on Apple's side.
I have a Synology DS218+ at home, and I have this issue with my MacBook Air recently updated to Sequoia.
I back up the same MacBook Air at work on a Western Digital My Cloud NAS, and I have precisely the same problem.
I have the impression it is triggered when I leave the computer unattended (inactivity? Sleep?), even if in the Battery panel I have ON the switch "Prevent automatic sleeping on power adapter when the display is off".
I tried only once an overnight backup on an external SSD, and next morning I found the red dot with the "i" in the Time Machine control panel and the message "backup could not complete because some files are not available...etc."
Hope they fix it in 15.0.1/15.1.
Sequoia Time Machine Synology NAS keeps disconnecting
