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Sequoia Time Machine Synology NAS keeps disconnecting

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

Posted on Sep 18, 2024 12:06 AM

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Posted on Oct 5, 2024 11:57 AM

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.

101 replies

Oct 21, 2024 12:22 AM in response to spoona

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

Oct 21, 2024 2:31 PM in response to BlueJayNE

Hi BlueJayNE,


I don't think it is related to MAC address selected, in my case I used fixed one and it works or fails just depending on having firewall enabled or disabled.


After reading your comment I have given a chance disabling the WIFI MAC address privacy and results remain the same, that is Time Machine Backup works or fails depending on the Firewall status.


Maybe others can try and share their experiences.

Oct 25, 2024 5:10 AM in response to spoona

Hi everybody.


Glad to hear other people are finding the firewall solution works.


Sadly, not the case here - my iMac Pro is still failing to complete backups with Time Machine reporting the networked Synology is disconnecting (it isn't). I've never had firewall turned on and it is most definitely turned off.


Apple never got back to me as they promised, so I guess I will need to start the whole task of raising the issue and having it escalated again.


Obviously, I will report back if there are any developments.

Oct 28, 2024 6:44 PM in response to donazipe

Upgrading from 15.0.1 to 15.1 today fixed it. Could create a new initial backup of about 250 GB within 2 hours. It failed 2 times during that, but always continued where it stopped and after completion a "verify backup" succeeded. Also a good new timemachine feature is the limitation to certain size when creating the initial backup in the advanced options. Previously that required quota settings on the shared folder which is now not needed anymore.

Oct 31, 2024 10:54 AM in response to spoona

Well that's odd - it's started working of its own accord.


Long-time readers might remember that my iMac Pro continued to report network disconnections after upgrading to 15.1. I forgot to disconnect the drive overnight, so the Mac tried to do another backup - which worked. And it's been quietly backing up every hour since.


So I think the 15.1 update does resolve this issue. Why I got an error? No idea, but I'll be glad to never see this again.

Oct 31, 2024 3:01 PM in response to spoona

I can now also confirm that 15.1 appears to have resolved the Time Machine/NAS issue completely.

Incidentally, I was also having what I thought was an unrelated issue with Mail being very slow to retrieve new messages, and that problem has also been resolved, so I wonder whether that was also related to a problem within the firewall.

Sequoia Time Machine Synology NAS keeps disconnecting

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