Sequoia Time Machine Synology NAS keeps disconnecting

After disabling the firewall and waiting for a successful backup to complete, I enabled the firewall again.

I was sure the next backup would fail, but it didn't and Time Machine completed several daily backups since.

The backup is still failing even if I add Time Machine to the native firewall exception to allow incoming traffic. It will work with the firewall turned off, but once it's back on, the backup will fail.

Bravo. I disabled MacOS Network Firewall and the backup immediately started running. Per some other posts with similar results, I will let it run a few days and then

1) re-enable firewall with current settings. if that fails again, I'll

2) re-enable firewall with updated settings to accommodate Time Machine settings.

Thanks much for the help

The issue is the Private WiFi Address for a WiFi Connection.

My WiFi subnet was 192.168.4.0/24, but I was getting an IP Address of 192.168.5.63 when connected. I was not able to browse or ping to any device on the 192.168.4.x subnet. I could not print either.

Turning off the "Private WiFi Address" and then disconnecting/reconnecting to my WiFi network resulting in getting a 192.168.4.x address and I was able to backup to my NAS and browse to it.

Same issue: Mac mini 2020 M1, Sequoia 15.1, Synology NAS

When this still didn't work with the updated MacOS 15.1 and turning the Firewall off, I tried a different tactic.

I shut down the Synology NAS

In Time Machine I selected a manual back-up. Time Machine responded that it could not find the server.

Restarted the NAS.

Again selected a manual back-up in Time Machine.

After some time "preparing the back-up", the backup actually began....and completed!

The Firewall was active the entire time.

Similar issue here on an iMac Pro running Sequoia and a Synology DS218j with the latest Desktop Manager 7.2.2-72806. The Synology is not reporting any problems.

My Time Machine backups initially worked after updating the Mac, but have now repeatedly failed and I haven't been able to get them running again. I've even created a new backup folder on the Synology to see if it is an incompatibility with previous backups.

I can get the backup started after a very long 'Preparing to back up...', it finds the changes and then begins copying files to the Synology, however it stops abruptly before being completed and never gets to the cleaning up stage.

I don't get any sort of pop-up alert warning, nor does the Mac itself say the Time Machine drive has disconnected, but the little red error symbol gives the same Time Machine error you're seeing about the disk disconnecting whilst in use. The drive remains mounted on the Desktop and in Finder.

Trying to Verify backups through Time Machine also results in the same error.

I've tried rebooting the Mac and the Synology but the error persists.

I wasn't getting this issue before the update to Sequoia, so something behind the scenes has definitely changed. Unfortunately, Time Machine's rather terse messages about what it is doing aren't helping me see where exactly things went wrong.

I fired up TheTimeMachineMechanic after a failed backup and its results are:

Analysis from 2024-09-21 12:22:24 +0100 to 2024-09-21 14:22:24 +0100 for 2 hours:

Backing up 1 volumes to Backups of Hekla (/dev/disk3s1,TMBackupOptions(rawValue: 0)): /Volumes/Backups of Hekla 2 on which there were 3.93 TB, 3.93 TB available.

Current free space on backup volumes: 0))

No auto backups started in the period, no backup has been completed successfully in the period,

Created 0 new backups, and deleted 0 old backups,

Created 1 new snapshots, and deleted 6 old snapshots,

Of 0 volume backups:

0 were full first backups,

0 were deep scans,

1 used FSEvents,

0 used snapshot diffs,

0 used consistency scans,

0 used cached events.

✅ No error messages found.

⚠️ Running check on scheduling system (CTS and DAS).

DAS appears to be rescoring normally over the last 90 minutes.

Running CTS check next.

CTS has not been told to run a backup in the last 90 minutes. Scheduling may have stopped.

Consider restarting your Mac.

Hopefully this is a teething trouble from a new OS release, but I might need to attach an SSD as a temporary backup drive until the issue is resolved by either Apple or Synology - though I think the only drive I have spare is one of those potentially flaky SanDisk portable drives :(

spoona wrote:

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:

https://discussions.apple.com/content/attachment/210afe65-c27a-4054-a7f0-293a6a494cf0

The backup will fail anywhere between one and five minutes after starting.

Locally macOS 13 and macOS 14 are working with Synology configured for Time Machine Server. DSM 7.2.2 with update. Testing included full restores.

Here is the Synology NAS setup (also linked in a reply above):

• https://kb.synology.com/en-global/DSM/tutorial/How_to_back_up_files_from_Mac_to_Synology_NAS_with_Time_Machine

If it is still not working, I’d suggest updating to current DSM if not already, and then asking this question again over in the Synology forums: https://community.synology.com/enu/

No macOS 15 in production yet (locally), so no Synology TM support testing (here).

Disabling the firewall on your Mac can indeed resolve issues with Time Machine backups, particularly when using a Synology NAS. Here’s how to do it and some additional context based on user experiences:Steps to Disable the Firewall on macOS

1. Open System Settings:Click on the Apple menu in the top-left corner of your screen.Select System Settings.
2. Navigate to Network Settings:In the sidebar, click on Network.Scroll down and click on Firewall.
3. Disable the Firewall:Click on the toggle to turn off the firewall.You may need to enter your admin password to make changes.
4. Test Time Machine Backup:After disabling the firewall, attempt to initiate a Time Machine backup again.Check if the backup completes successfully without interruptions.

Additional Considerations

• Firewall Rules: If you prefer to keep the firewall enabled for security reasons, consider setting specific rules to allow Time Machine traffic. This can often be done by allowing connections for specific services or applications related to Time Machine.
• Network Configuration: Ensure that your Synology NAS is properly configured for Time Machine. This includes enabling SMB (as AFP is deprecated) and ensuring that your NAS is accessible from your Mac without restrictions.
• User Permissions: Verify that the user account you are using has appropriate permissions to access the Time Machine share on your NAS.

User Experiences

Many users have reported that disabling the firewall resolved their backup issues, as it allowed Time Machine to communicate freely with the NAS. However, it's advisable to re-enable the firewall after testing and configure it correctly to maintain network security.If you continue facing issues even after disabling the firewall, consider checking other network settings or consulting Synology's support documentation for further troubleshooting steps.

Interesting. And I should add I am running a Macbook Pro M1 so the macOS 15 for Intel seems suspicious.

Wow nice… will be neat if I don’t have to delete my backup history every year. Thanks for posting that!

Update: No. 15.0.1 did not solve the problem. The problem re-occurred today.

I installed the recommended Synology beta for SMB and my backup continued to fail. The only workaround I've found to work consistently is to turn the firewall off.

Simply go to System preferences, Open the Network item and in Firewall, toggle it to off, and your backups will work. Of course, it's not ideal if that's the only firewall protecting your machine.

I'm running 15.0.1 with firewall turned on, but my TM backup is still failing, if you turned it off, it will work, but not ideal. Anyone figured out how to get it back working with firewall on?

As disabling Apple's firewall seems to fix the issue, this is clearly not a Synology problem to fix.

Apple did some changes to the firewall settings that are causing the problem.