What is VSS?
+VSS is a subsystem within Windows to help manage taking point-in-time snapshots of data and applications.
Can Comet back up open files?
+Comet can back up open files using VSS with the "File and Folder" protected item type when you enable the "Take filesystem snapshot" checkbox. The separate Application-Aware Writer booster is for other installed applications that provide a VSS Writer driver. You do not need the Application-Aware Writer booster to back up open files with Comet.
What is a VSS Writer?
+A VSS Writer is a driver that is integrated with the VSS subsystem in Windows, to allow a backup job to be fully consistent with an application’s state. When you select a VSS Writer in Comet's "Application-Aware Writer" Protected Item type, Comet asks the VSS writer to produce an application-consistent backup of all its specific application data that is then made available to Comet.
What applications can I back up via a VSS Writer?
+Microsoft SQL Server, Microsoft SharePoint, Microsoft Exchange Server, Microsoft Hyper-V, Oracle DB, and many more third-party applications all ship a VSS Writer driver with their product. By using the "Application-Aware Writer" Protected Item type in Comet, you can back up data from these applications in an application-consistent way.