This Knowledgebase article provides information about how Neverfail supports Volume Shadow Copy Service (VSS).
Neverfail does support Microsoft Volume Shadow Copy Service (VSS) running on both the active as well as the passive server. However, VSS backup images can only be accessed from the active Server. To access VSS backups on the passive server, you must first perform a manual switchover. Refer to the Neverfail Reference Guide for assistance on performing a switchover.