Veeam is very unstable and hangs server

This can be lack of memory or cpu during the operation. Or smething related to the VBR database, but it's hard to know.
Did you open a support case with Veeam? The support team should be able to help.

Hi ​@matt-man -

Eeek...sorry to hear you’re having issues there. The 1st and foremost suggestion is to contact Support. They’re really your best bet to get (hopefully) to a stable state. I see you’re not looking at suggestions for scrapping what you’re migrating to, but honestly...Win2025 is too new to migrate to, including with using ReFS. With the time you’re spending troubleshooting, you could go back to Win2022 server and have a more stable setup. That would be my recommendation, aside from getting ahold of Support to see if they can rectify the issues you’re experiencing with Win2025.

Maybe someone else has a differet suggestion. Not sure if logs can tell you anything for Veeam (C:\ProgramData\Veeam\Backup and Replication), or for Windows...event viewer.

Keep us posted.

Best.

I have found that Win2025 is not at the stage yet to run Veeam on it and have stuck with Win2022.  Hopefully support can sort things out.

1- It doubt that it is a problem with CPU or memory.  Currently there are 24 cores assigned to that VM, as for the memory, 64GB is allocated and I can expand that to 750GB, but I really doubt it is the problem.

2- Server-2025…. the problem is that I needed to upgrade another machine to Server-2025.   Having done that, I also wanted to backup that new server to the Veeam repository.   It was my understanding that I needed to upgrade the backup server so it can backup the new Server-2025.   So going back to 2019 (prev version I was using) is not possible unless I don’t want to backup the Server-2025 machine.

3- I’ve opened a support ticket, but no response yet.

4- I disabled veeam completely on the backup server, and I’m trying to migrate the data on the ReFS filesystem to a standard NTFS file system.. When that is done, I will try to rescan the repositories and see what happens.

​@matt-man - ok, keep us posted. 

​@matt-man 

Hi, hopefully you didn’t run Windows Upgrade instead of a fresh re-installation of VBR with Windows Server 2025. I have a 100% “failure” quote with Windows Upgrades (instead of clean, new installations) in context of Veeam (primarily on VBR but I could imagine having trouble with ReFS after upgrades since the ReFS version might change in Win Server 2025).

Going with support would be the best way but also make sure your VBR is up to date, all the credentials are up to date and the ReFS repo (different machine or VBR all-in-one?) is properly set, which in case of a hardware server means applying proper performance policies in the BIOS etc.

On the VBR also make sure that the PGSQL is optimized:

https://helpcenter.veeam.com/docs/backup/vsphere/postgresql_instance_configuration.html?ver=120

With all that done you only have two options imo:

1. re-install Windows OS on both systems (you should have the OS disks separated form the data disks anyways) and try again after a VBR config restore
2. wait for support response

I do have around 5 customers with Windows Server 2025 without any issues but we handles this as greenfield projects so we didn’t upgrade at all. Performance is also similar to the previous setups.

Please keep us posted to see what the support feedback is for potential future cases with Win Server 2025.

Best

Lukas

1- These were clean/new Srvr-2025 installs.

2- OS is typically on the C-drive, data is D: E: etc

3- ReFS is the default FS that Veeam wants to use… if there are issues with ReFS on 2025, they should either put out a warning or not make it default.

4- I’m currently moving data from ReFS to NTFS… looks like this process will take all day.

5- will check PGSQL after this manual move process is complete

Yeah..for any “synthetic” storage operations (synthetic fulls, merging), it is best to use a block clone technology like ReFS (Windows) or XFS (Linux). Makes those tasks go wayyyy quicker. Other than that, no real benefit of using ReFS over NTFS. 

Moving from ReFS to NTFS will take forever since all ReFS pointers have to be re-calculated and “deleted” to be applicable to NTFS so this should not be the way to go. If this is because of your issues I understand.

Please keep us posted what support says.

Interesting that it points to ReFS and MS still has issues there.  Great to hear you got things going well and keep us posted if support gets back to you.

Thanks for the update ​@matt-man . I’ve heard ReFS get stable after like Win2016, but before then heard so many bad data loss stories, I just stayed away from it and instead trained heavy on Linux and just implemented Block Cloning on XFS. Easy-peezy. Since it’s MS, not surprised to hear issues with ReFS have resurfaced in Win2025. 

Glad you seem to have got it sorted though. Keep us posted how the rest goes.

Best.