What is Volume Shadow Copy Service (VSS) ?

VSS is a framework that facilitates communication between applications, storage subsystems, and storage management applications (including backup applications). This framework enables you to define, persist, and use point-in-time copies of storage data.The Windows SharePoint Services VSS Writer is a new service in Office SharePoint Server 2007 and in the server products in the 2007 Office release. This writer service enables a requestor to ask a front-end Web server to provide a VSS backup (full or differential), and Office SharePoint Server 2007 then points the requestor to the SQL databases and the search index to be backed up by using VSSThe Volume Shadow Copy Service (VSS) is a set of COM interfaces that implements a framework to allow volume backups to be performed while applications on a system continue to write to the volumes. Volume Shadow Copy Service (VSS) was introduced in Windows XP and Windows Server 2003.