Confirmation of vMotion Behavior During Backup Processing in VBR v12.x and v13.x

[rin]

Hi,
 
I found the following forum post regarding vMotion and Veeam Backup & Replication:
viewtopic.php?f=24&t=68186&start=0
 
In this post, it is stated that:

- If a VM is already being processed by Veeam, vMotion/Storage vMotion is blocked (except for certain VMware Cloud environments).
- If vMotion is already in progress and Veeam cannot create a snapshot, Veeam will retry the operation.

Could you please confirm whether this behavior is still valid and supported in Veeam Backup & Replication v12.x and v13.x?

Additionally, if there have been any changes to this behavior in recent versions, could you please provide the current expected behavior?

If there is any official documentation or KB article describing this behavior, we would appreciate it if you could share it as well.

Thank you.
Rin

[david.domask]

Hi rin,

Yes, the behavior is still real, but I will make a more accurate statement:

"When performing backups using VDDK, part of the VDDK process is to temporarily disable vMotion during the scope of the backup, and re-enable it when completed"

It's not the backup application itself blocking it, this is part of the VDDK workflow required by VMware.

We do not document this as it's standard behavior from VMware; regrettably the VDDK documentation has been removed from public view by VMware, but if you're able to locate a copy of it you will find the necessary documentation.

And yes, if we cannot process the VM because it's participating in vMotion, we will retry it later.

[rin]

Hi domask,
 
Thank you for the clarification.
I have reviewed the VDDK-related entries in the backup logs and would like to confirm two additional points.
 
During the backup job, I observed the following functions being called:
1. At the beginning of VM processing:

VixDiskLib_PrepareForAccess
[24.09.2026 21:21:47.901] <12828> vdl | [vddk] VixDiskLib: VixDiskLib_PrepareForAccess: Prepare to access disk.

2. At the end of VM processing:

VixDiskLib_EndAccess
[24.09.2026 21:34:11.631] <20388> vdl | [vddk] VixDiskLib: VixDiskLib_EndAccess: Disk access completed.


Regarding your previous statement:
"When performing backups using VDDK, part of the VDDK process is to temporarily disable vMotion during the scope of the backup, and re-enable it when completed."
 
Could you please confirm whether the VDDK operations you referred to are specifically the following?

- VixDiskLib_PrepareForAccess temporarily disables the relevant migration operation during VM processing.
- VixDiskLib_EndAccess re-enables the operation after VM processing is completed.

If so, could you also clarify exactly which migration operations are prevented by these functions?


In particular, does VixDiskLib_PrepareForAccess prevent both of the following operations?

- Compute vMotion, where only the ESXi host is changed
- Storage vMotion, where the VM files are moved to another datastore

I found information suggesting that Storage vMotion is prevented, but it is unclear whether regular Compute vMotion for a powered-on VM is also prevented.
 
Therefore, I would appreciate explicit confirmation of whether regular Compute vMotion is actually blocked while Veeam is processing the VM.
 
Thank you.
Rin

[david.domask]

{quote]Could you please confirm whether the VDDK operations you referred to are specifically the following?

- VixDiskLib_PrepareForAccess temporarily disables the relevant migration operation during VM processing.
- VixDiskLib_EndAccess re-enables the operation after VM processing is completed.[/quote]

Correct, it's those lines.

I found information suggesting that Storage vMotion is prevented, but it is unclear whether regular Compute vMotion for a powered-on VM is also prevented.

It's about relocating the virtual disks, so Storage vMotion.