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VM quiescing can be tested by running the following powercli command.
I would suggest running this against the same VM and seeing if this completes or not. If it does complete, then there is possibly an issue with your backup solution / backup agent installed on the VM if applicable.
Now to your questions:
Is the error valid
Yes, probably. if you have applications such as SQL, Exchange on the VM then you will need to quiesce those as part of the backup job to ensure that they are in a consistent state while the backup copies the files. This would ensure that the backups for those applications are recoverable.
Can I trust backups / replication
Possibly, if you do not have those kinds of applications that require quiescing on any of your VMs, then there might not be a need to worry about this error.
Disable quiesce
Again, probably okay if your applications do not require this to happen upon getting backed up. If they do, some restores might work because the apps were already in a state ready for backup, but you run the risk of some restores not working.
Correct forum
Sure, it's a possible vSphere issue that you are experiencing.
More information from official KB:
- Quiesce: If the flag is 1 or true, and the virtual machine is powered on when the snapshot is taken, VMware Tools is used to quiesce the file system in the virtual machine. Quiescing a file system is a process of bringing the on-disk data of a physical or virtual computer into a state suitable for backups. This process might include such operations as flushing dirty buffers from the operating system's in-memory cache to disk, or other higher-level application-specific tasks.
Note: Quiescing indicates pausing or altering the state of running processes on a computer, particularly those that might modify information stored on disk during a backup, to guarantee a consistent and usable backup. Quiescing is not necessary for memory snapshots; it is used primarily for backups. - Source: VMware Knowledge Base
