After backup my VM is frozen

U

Unimatrix001

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May 19, 2025
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Hello there, my first post here.

I have a Windows Server 2016 VM which runs my SQL server and everything runs fine until backup. I have a backup plan which backs up my VM once a week (over the weekend) and after that my VM becomes unresponsive.

When I go to the Summary section of my VM where the IP address should be it says "guest agent not running" and there is no IP address. Through the Console I only see Login screen but it is not responsive. Remote desktop also doesn't work. The only thing that works is hard reset after which everything works fine until next backup.

Besides this VM I have few more (Linux and Windows) VM's which back up normally.

Proxmox VE version is 8.4.1.

I am novice to whole Proxmox and Linux environment so have patience :)

Kind regards,
Vedran
 
Hmm looks goot to me. 2 things: You have NUMA enabled? So it's a multi-socket CPU system? Did you try the backup without any redirecting USB device?

EDIT: How do you run your backup? Integrated backup option? PBS? Third party software?
 
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devaux said:
Hmm looks goot to me. 2 things: You have NUMA enabled? So it's a multi-socket CPU system? Did you try the backup without any redirecting USB device?

EDIT: How do you run your backup? Integrated backup option? PBS? Third party software?
Click to expand...
Yes, it's a Lenovo two socket CPU system. That USB device is used for daily SQL database backups from within VM.

I use Proxmox integrated backup option.
 
Unimatrix001 said:
Yes, it's a Lenovo two socket CPU system. That USB device is used for daily SQL database backups from within VM.

I use Proxmox integrated backup option.
Click to expand...
Do you have the possibility of performing the backup while the USB hard disk is NOT being passed through to the VM?
 
What backup mode do you use? Have you tried Stop instead? Have you tried enabling Fleecing?

EDIT: I'm not sure if I have to say this explicitly: can you please try and see what happens when you use Stop and also when you enable Fleecing.
 
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If backup destination is too slow,
I/O is delayed up to timeout, then VM crash.
Be careful to not overlap within guest backup and pve backup.
By the way, PVE do VSS snapshot which, by default, break existing SQL chained backups (diff backup), this topic explain VSS options.
There is no problem if within guest SQL backups are only full.
 
_gabriel said:
If backup destination is too slow,
I/O is delayed up to timeout, then VM crash.
Be careful to not overlap within guest backup and pve backup.
By the way, PVE do VSS snapshot which, by default, break existing SQL chained backups (diff backup), this topic explain VSS options.
There is no problem if within guest SQL backups are only full.
Click to expand...
It only happens at the end of backup and I get email notification that backup is successful. I do have backup within another guest that overlaps with PVE backup, do you think this is can be the problem or only if backup is within guest and the same VM is being backed up? I do hope you understand my question.

My SQL backups are full type.
 
Maybe try the Stop mode, at least you'll be sure that all data is at rest and the backup is complete. Maybe try Fleecing, to see if this prevents a hick-up or delay during backup.
 
leesteken said:
Maybe try the Stop mode, at least you'll be sure that all data is at rest and the backup is complete
Click to expand...
Not really, because "Stop mode" shutdown VM, do snapshot, start backup, then immediately start VM, backup continue as background, so I/O stress can exist.
I was impacted sometimes ago with ZFS on slow 2'5 HDD, some services at VM restart did not start correctly, like SQL... disk was replaced but since this time, I'd set scheduled VM shutdown, backup fully offline, then hook script to restart VM.
 
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_gabriel said:
Not really, because "Stop mode" shutdown VM, do snapshot, then immediately start VM, so I/O stress can be occurs.
Click to expand...
Thank you for pointing this out. Nevertheless, it would be interesting whether Stop would not cause problems (as the USB would disconnect on a stopped VM). Also, whether enabling Fleecing (with Suspend or Stop) would help, is interesting. I hoped that my question about the backup mode the first time would trigger @Unimatrix001 to try both things but since it did not, I asked explicitly a second time. More data points won't hurt, right?
 
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