This issue can cause FT failover failure, as the result, Virtual Machine is actually not under the FT protection even though vCenter UI shows FT status as "Active".
When Virtual Machine is configured with VM Namespace and "namespaceMgr.dbFile" is present in the Virtual Machine config file, Fault Tolerance (FT) failover cannot succeed in resuming FT Secondary Virtual Machine, below error messages show in vmware.log of FT Secondary Virtual Machine:
vmx - NamespaceMgrCheckpoint: No valid database found while restoring the namespace fields.
vmx - Msg_Question:
In(05) vmx - [msg.checkpoint.restoregroup.failed] An error occurred while restoring the virtual machine state from file "(null)".
vmx - [msg.checkpoint.resume.error] An error caused the resume operation to fail. Preserve the suspended state and correct the error, or discard the suspended state.
This is caused by inter-operational issue between FT and VM Namespace DB, as FT is not capable of replicating VM Namespace data from FT Primary VM to FT Secondary VM, and there is a lack of prevention for FT turn-on or for VM Namespace operations when another has been enabled.
Currently there is no resolution on the issue. This will be fixed in the future release.
To workaround the issue, please follow the below:
Before turning on FT, the components/products that could possibly create or use VM Namespace need to be disabled on the VM, including SDMP, vgauthImport, Appdefense, NSX and Guest Customization for Instant Clone.
The "namespaceMgr.dbFile" config setting needs to be removed from VM config file.