Comparing IBM Storage Protect and Ntbackup.exe interaction with VSS
Using the Ntbackup.exe executable file does not fully utilize Volume Shadow Copy Services (VSS) and cannot always be considered as a benchmark for IBM Storage Protect interaction with VSS.
The known difference between Ntbackup.exe and IBM Storage Protect in the context of VSS is that Ntbackup.exe does not use VSS to back up the Active Directory (NTDS). Although Ntbackup.exe uses VSS to take a snapshot, it still uses the legacy NTDS backup API to read data from the disk. IBM Storage Protect uses the VSS interface to read NTDS data from the disk. If there is a problem with the VSS writer responsible for NTDS, it does not reveal itself with Ntbackup.exe.
Issue the VSSADMIN LIST command to query the VSS writer state to ensure that VSS is in a stable or ready state.