IVssHardwareSnapshotProvider::OnLunEmpty method (vsprov.h)

The OnLunEmpty method is called whenever VSS determines that a shadow copy LUN contains no interesting data. All shadow copies have been deleted (which also causes deletion of the LUN.) The LUN resources may be reclaimed by the provider and reused for another purpose. VSS will dismount any affected volumes. A provider should not issue a rescan during OnLunEmpty. VSS will handle this cleanup.

Syntax

HRESULT OnLunEmpty(
  [in] VSS_PWSZ            wszDeviceName,
  [in] VDS_LUN_INFORMATION *pInformation
);

Parameters

[in] wszDeviceName

Device corresponding to the LUN that contains the shadow copy to be deleted.

[in] pInformation

Pointer to a VDS_LUN_INFORMATION structure containing information about the LUN containing the shadow copy to be deleted.

Return value

This method can return one of these values.

Remarks

Hardware providers should delete a shadow copy and reclaim the LUN if and only if
OnLunEmpty is being called. A hardware shadow copy may be used as the backup media itself, therefore the LUNs should be treated with the same care the storage array treats LUNs used for regular disks. Reclaiming LUNs outside of processing for OnLunEmpty should be limited to emergency or an administrator performing explicit action manually.

In the case of persistent shadow copies, the requester deletes the shadow copy when it is no longer needed. In the case of nonpersistent auto-release shadow copies, the VSS service deletes the shadow copy when the requester calls IUnknown::Release on the IVssBackupComponents object. In the case of nonpersistent non-auto-release shadow copies, the VSS service deletes the shadow copy when the computer is restarted. In all cases, the VSS service calls the provider's OnLunEmpty method as needed for each shadow copy LUN.

Note that OnLunEmpty is called on a best effort basis. VSS invokes the method only when the LUN is guaranteed to be empty. There may be many cases where the LUN is empty but VSS is unable to detect this due to errors or external circumstances. In this case, the user should use storage management software to clear this state.

Some examples:

• When a shadow copy LUN is moved to a different host but not actually transported or imported through VSS, then that LUN appears as any other LUN, and volumes can be simply deleted without any notification of VSS.
• A crash or unexpected reboot in the middle of a shadow copy creation.
• A canceled import.

Requirements

See also

IVssHardwareSnapshotProvider