Timemachine Back-up in MacOS 26 (Tahoe) does not work on Synology DS920+ NAS

The solution proposed by karel250 worked like a charm. I had the letter "ä" on the volume. An ordinary letter in Swedish but not in English. I changed it to the letter "a". Fixed my time mashine.

Thanks you karel250.

Yes, this worked (karel250)! In czech language system set the route in the .spuresbundle to "Záloha svazku ......" I rename this to "Zaloha svazku...." and TM worked.

Apple have to fix this problem. System automaticaly create route "Backuf of......." translated by language setting with diacritic. It make a problem.

[Precheck]

Please kindly follow the steps below to change settings on your Mac.

1. Open Terminal on macOS, and edit /etc/nsmb.conf with vi:

• • sudo vi /etc/nsmb.conf

1. Change the value of signing_required from no to yes:

• signing_required=yes
  • 

1. Press the Esc key, then type ZZ or :wq to save the changes and exit vi.
2. Reboot your Mac.

Once you have completed the steps above on your Mac, please continue with the steps below to check settings on both your NAS and Mac.

[On your Synology NAS]

1. Ensure that DSM is properly configured for Time Machine backups. Try creating a new shared folder and set it as the Time Machine backup folder, rather than using the original one.
2. Ensure your NAS has enough free space.
3. Make sure the following options are selected in Control Panel > File Services > SMB > Advanced Settings > General:

• Maximum SMB protocol: SMB3
  • Note: Time Machine backups require SMB3, so please change it back to SMB3 if it was modified.
  • Enable Opportunistic Locking
  • Enable SMB2 Lease
  • Enable SMB Durable Handles (Cross-protocol file locking will be disabled)

1. Confirm the following options are enabled or properly set in Control Panel > File Services > Advanced> Bonjour:

• • Enable Bonjour service discovery to locate Synology NAS
  • Enable Bonjour Time Machine broadcast via SMB
  • Set Time Machine Folders

It works!

The secret was to open the sparsbundle in disk utilities, where I found a longer name for the spartsbundle, where our Swedish characters were used. Exchange those characters to anything else in the span of a-z, hit return, and try two more TM-backups. The second one flies as the wind! Beautiful! Thanks all!

THANK YOU!! The real solution for me was to RENAME the APFS Drive! Thank you SuperMek_original!

I was struggling in the last two weeks to make it work. I tried everything including the solution marked as the famous. That DOES NOT worked for me! Only the renaming worked because my APFS disk name is had also contained special characters like () and áéöő. So I renamed it to TimeMachineHP with the disk manager and immediately started to work. Thank you!

Sharing is caring.. There is a bug in Samba versions 4.21-4.22 that conflicts with Tahoe for Time Machine. It is the current version at the time of this writing. It should be fixed in 4.23, or if you can downgrade to 4.20 it was successful for me.

https://bugzilla.samba.org/show_bug.cgi?id=15926

Finally figured this out. It took me a while to realize where to change:

The name of the backup disk will have its name set in the language used in your OS. In Sweden it will be "Säkerhetskopior av [your computer name]". And when I changed that ä to an a it worked although not immediately. I started the Time Machine backup but told me the backup disk was already in use so I unmounted the disk and started the backup again and voila!

I hope it helps.

I'm just worried that this workaround will break when Apple fixes this?

Hi all,

I have been facing the same trouble during the backup - my disc was disconnected. I opened the disk utility as another user in this conversation and I found the backup image bundle name "Zálohy svazku ..." has in it's name the letter "á", so I renamed it to "Zalohy svazku ..." and now the time machine backup works.

I have a Synology DS223j configured based on Synology's kbase article, and it's backing up my 16" M4 Pro MacBook Pro running macOS 26 just fine, and has been doing so since I installed Tahoe yesterday. Last backup completed a few minutes ago.

Have you tried restarting the NAS?

Thanks for your answer. I did reboot the DS920+ and it did not work.

Next try was to kill AFP and tested it again. Now the DS902Plus share is shown in Network and Finder, but an error was shown. IP-adres not available or something.

On my iPhone and iPad I can login at the NAS and I can access shares and files, but on MacOS Tahoe I still get no permission.

The Synology-assistent.app shows the Root Share DS920Plus and redirects via Safari to the Webportal, on which I can login.

Can you post the link to this kansen article, because I’m not sure I have configured the setting right.

Now I have SMB only and AFP disabled and the Share is shown up.

Finder and TimeMachine does not find the IP-Adress for DS920Plus.

willem-blues wrote:

Can you post the link to this kansen article, because I’m not sure I have configured the setting right.

Now I have SMB only and AFP disabled and the Share is shown up.

Finder and TimeMachine does not find the IP-Adress for DS920Plus.

I used the same article as the link in your original post. If it helps, here are my settings for the NAS.

[Edited by Moderator]

Hello,

I have the same problem with a new clean installation of macOS Tahoe 26. I back up data not only to Synology but also to Truenas, using the SMB protocol in both cases. Backups do not work in either Synology or TrueNAS. The backup stops at the "Preparing" stage, regardless of whether encryption, username, or password is enabled. On my other laptop with macOS Sequoia 15.7, backing up using the SMB protocol works without any problems.

Also on the previous version of MacOS I had problems using my Synology for Time Machine backups. My MacBookPro M1 would loose connection to the NAS every time it came back from sleep. I fixed this installing Automounter, since then I had no problems. Until Tahoe.....

In order to have Time Machine backups with Tahoe on my Synology I had to start from scratch...

I’m experiencing the same issue – Time Machine shows the following error: “Time Machine can’t complete the backup to ‘Time Machine’. The backup disk is not available. Make sure it is connected or select a different backup disk.”

Regular connection to the NAS disk over the network works fine. However, after the update, direct access to the NAS via the Finder sidebar (where I had created a shortcut pointing directly to a specific folder on the NAS) also stopped working, even though it used to work before. Creating a completely new backup on a new disk on my Synology NAS (DS418) did not help either.