Backups failing when using Netvault HyperV Plugin and Microsoft Clustered Shared Volume support. (4045117)

Backups fail with errors;

Error Date/Time 48 Data Plugin Client Name Error creating VSS snapshot

Error Date/Time48 Data Plugin Client Name Failed to backup VM

Error Date/Time 48 Jobs Server Name Job Status: Backup Failed
 

Currently you can only do Clustered Shared Volume (CSV) backups from co-ordinator node safely. All other nodes in the cluster that are not the owner of the Physical Disk resource conduct data access through a new Microsoft technique that is referred to as "Direct I/O".

Direct I/O is the process used by CSV to perform I/O operations from a VM to the storage device with enhanced performance. This is accomplished by splitting the transaction and sending NTFS metadata operations to the coordination node over the network while sending data I/O directly to the disk class driver for the storage device. By sending data directly from a file system mini-filter driver called CSVFilter.sys to the disk class driver, CSV bypasses all local file system and volume/partition processing on non-coordination nodes. This includes the VSS infrastructure, resulting in CSV and Direct I/O being incompatible with the environment required by the VSS infrastructure. A backup cannot be initiated by a Requester on a non-coordination node.

To make the task simple for a Requester, a new Microsoft Cluster API has been introduced. ClusterPrepareSharedVolumeForBackup is introduced in Windows Server 2008 R2. After a Requester initializes the snapshot set by calling StartSnapshotSet, it needs to call the new ClusterPrepareSharedVolumeForBackup. This new API replaces existing Win32 API's for discovering the path to volumes


ClusterPrepareSharedVolumeForBackup will provide the following behavior:

1. The volume will be moved locally to the node where the Requester is initiating the backup. This will allow the VSS infrastructure to be involved, and the backup to be successful.

2. Re-directed I/O will be enabled so that all I/O is sent over the network and synchronized by the coordination node

3. Completion of the backup will be tracked. Once the backup operation is complete, re-directed I/O will automatically be disabled and t

The use of the Netvault HyperV Plugin with Clustered Shared Volumes is not currently supported.

To allow backup applications to resolve CSV files to volumes and then to prepare the volume for backup, the following externally visible (published and documented) APIs are available:

- ClusterIsPathOnSharedVolume

- ClusterGetVolumePathName

- ClusterGetVolumeNameForVolumeMountPoint

- ClusterPrepareSharedVolumeForBackup

ClusterClearBackupStateForSharedVolume