Question about backup when VHD is on a RAM disk

[staffIDS]

Good morning,

I have Windows Server 2016 with Hyper-V and
Veeam Backup & Replication v11.0.0.837 P20210525 and
I have open the Case #05764694

There is a virtual server with this configuration:
Disk C: 50 GB on Samsung SSD 870 EVO 2TB
Disk S: 500 GB on Samsung SSD 870 EVO 2TB
Disk R: 16,5 GB on Ram Disk 17 GB done with StarWind RAM Disk (no more free RAM)

On disk R: there is a MS SQL TEMPDB with size 16 GB because write so much and the SSD will die in less 1 year

But when the backup start, the disk R: go in low space and the backup failed

02/12/2022 21:17:50 :: Production drive R:\ is getting low on free space (399 MB left), and may run out of free disk space completely due to open snapshots.
02/12/2022 21:17:51 :: Error: Insufficient free disk space on production drive R:\.
02/12/2022 21:17:51 :: Processing finished with errors at 22/11/2022 21:17:51

So I tried a workaround with the Symbolic Link:
mklink "S:\Hyper-V\Virtual Hard Disks\RamDisk.vhdx" R:\RamDisk.vhdx
And in the Hyper-V disk path there is S:\Hyper-V\Virtual Hard Disks\RamDisk.vhdx
It works fine and the AVHDX for the backup should be created on disk S: (with more free space)

But the backup failed with this error:

03/12/2022 23:41:01 :: Error: Failed to call RPC function 'HvGetVolumesByPaths': Il file o la directory non costituisce un reparse point. Failed to retrieve reparse point data.
03/12/2022 23:41:01 :: Processing finished with errors at 03/12/2022 23:41:01

Do you have any suggestion or alternative solution?

Thanks in advance and best regards

Michele

[HannesK]

Hello,
and welcome to the forums.

Foreword: Logs are missing, so support won't be able to help

A few ideas from my side
1) increase the RAM disk to have enough free space (at least 2GB - there is a registry key do manipulate that value, but I'm not comfortable trying it out on a SQL server). If you don't have more RAM, make the RAMdisk smaller do have more space (I have never heard, that a RAMdisk is the solution to save SSDs, but the hardware sounds like consumer hardware, so that might be different). There is also a global setting for free disk space, but with only a few hundred MB free, the software might still not do it.
2) Veeam works with VSS snapshots. Can you create VSS snapshots of all disks from inside the VM?

Best regards,
Hannes

[staffIDS]

Thanks Hannes,

the server is with 64 GB RAM and the Virtual Machine use 32 GB.
So the first solution is the only solution, but now we have put more RAM.
Now with 144 GB RAM all works fine

Best regards