Unknown change epoch error in ESX hostd.log may appear on VMware backup with NFS datastore

Problem

When attempting to run a VMware backup using CBT ( Change Block Tracking  ) and if the VMware client is located on a NFS type datastore with the configuration as below, you may see an error message "Unknown change epoch"  in hostd.log on ESX server.

[  VMware Backup Configuration ]

1)   NetBackup VMware backup Full and Incremental / Differential schedule type
2)   Enable CBT (  Block Level Incremental is ON in VMware backup policy )
3)   Virtual disk of VMware client  is located on NFS type datastore








 

Error Message

NetBackup VMware backup job is completed successfully without errors in NetBackup logs. The following error message may be logged in hostd.log on ESX server.

[ hostd.log ]

error hostd[2A6CDB70] [Originator@6876 sub=Vmsvc.vm:/vmfs/volumes/0946c8d1-9fe20b09/xxxxxxxx/xxxxxxxx.vmx opID=33c9eca2-91-1ec1 user=vpxuser:VSPHERE.LOCAL\Administrator] Cannot compute changes for disk /vmfs/volumes/0946c8d1-9fe20b09/xxxxxxxx/xxxxxxxx.vmdk: Unknown change epoch.

Solution

NetBackup support VMware CBT backup on NFS type datastore. This error message in hostd.log does not impact the ability of NetBackup VMware backup. You can ignore this error message.