One or more snapshots are present on a VM, impacting performance.
Cause
When Veeam Backup & Replication begins a backup or replication job, it sends a VIM API command to the vCenter (or standalone host) to create a snapshot with the name "VEEAM BACKUP TEMPORARY SNAPSHOT ". At the end of the backup or replication job, Veeam Backup & Replication sends another API command to remove that snapshot. In some cases, this command will not be received, or in rarer cases it will not be executed.
This can be due to network connectivity issues between the Veeam Backup & Replication server and the vCenter, connectivity issues between the vCenter and the ESXi host, or more rarely due to a malfunction on the vCenter or host.
If the backup job did not complete due to power loss or failure of the Veeam Backup Service, the snapshot removal command will not be sent.
Solution
If these snapshots are present when the backup or replication job is not running, they can be safely removed using the Delete or Delete All buttons in the Snapshot Manager.
In some cases, the snapshot removal will produce an error in vSphere. When that happens you should perform troubleshooting based on the error message, or contact VMware support. If the failure to remove the snapshot involves a file lock and you are using the Virtual Appliance transport mode, make sure that the VM disks were removed from the proxy (KB1775).
If there are no error messages, this may be an infrastructure issue. Perform the following steps to identify the source of the issue:
During the backup job run continuous pings between the Veeam B&R server and the vCenter, or between the Veeam B&R server and the affected host, to determine if packet loss is indicated.
Observe resource usage on the Veeam B&R server and on the vCenter server to see if, for example, memory usage is very high.
Check event logs on the Veeam server and vCenter server.
More information
Do not delete this snapshot until the job is completed.
In version 6.5.0.128 and later, Veeam Backup & Replication tracks all snapshots it creates and tries to remove those snapshots on later job runs. Prior to 6.5.0.144, this feature could result in vCenter connection duplication if the temporary snapshot was deleted manually.
If the snapshot is named anything other than "VEEAM BACKUP TEMPORARY SNAPSHOT" then this KB is not applicable.