New VSS Support Added in vSphere 6.5

The vSphere 6.5 release included additional volume shadow-copy service (VSS) configurations and features. To support these new configuration and for more granular control over Windows guest OS quiescing, the function CreateSnapshotEx_Task was added to the 6.5 vSphere API, superseding CreateSnapshot_Task. CreateSnapshotEx_Task takes a quiesceSpec parameter, of type VirtualMachineGuestQuiesceSpec or VirtualMachineWindowsQuiesceSpec. The latter type can specify several important fields such as:

• vssBackupType – VSS_BT_COPY was previously used as the default for CreateSnapshot_Task but now VSS_BT_FULL, VSS_BT_INCREMENTAL, VSS_BT_DIFFERENTIAL, and VSS_BT_LOG are available also. Log truncation may be triggered according to application settings.
• vssBackupContext – this was introduced to enforce application (context VSS_CTX_BACKUP) quiescing or file system (context VSS_CTX_FILE_SHARE_BACKUP) quiescing.
• The timeout (default 15 minutes) for quiescing virtual machines can now be configured anywhere from five minutes to four hours.

CreateSnapshotEx_Task requires VMware Tools 10.1.0 or higher installed on the backed-up virtual machine.