Incremental restore of vmdk from Symantec Netbackup is corrupted.

During restore tests one of the critical MSSQL VM failed to restore from incremental Symantec Netbackup backup.  We were able to restore successfuly VM from full backup.

Restoring from incremental backup lead to corrupted state of Windows.

We checked any leftover snapshots, cleaned up the VM directory.

The key thing was VMtools version. The current ESXi build is
ESXi 5.1.0 Update 1 build-1312873. 

VMtools version installed inside affected MSSQL VM - 9.0.0.15210 – esx5.1 GA (799733), the recommended version of VMtools 9.0.5.21789 - esx5.1p03 (1312873).

Please check: http://packages.vmware.com/tools/versions

The virtual hardware version of MSSQL VM:

virtualHW.version = "8"

Based on http://blogs.vmware.com/vsphere/2013/02/clarification-on-zero-down-time-vmware-tools-uprade-in-vsphere-5-1.html

Zero-downtime VMtools upgrade is possible on virtualHW 9 or higher.

In this case reboot was required to get all new features of VMtools.

We scheduled maintenance window with MSSQL DBA, upgraded VMtools and test restore from incremental backup - it finished SUCCESSFULLY we can login into VM GuestOS without any issue.