Several methods and scenarios exist for mirroring data between geographically separate sites. Each method has its own strengths and weaknesses. For a Business Continuity Clustering system, you need to choose either host-based mirroring or storage-based mirroring (also called array-based mirroring) and whether you want the mirroring to be synchronous or asynchronous.
Figure D-1 Synchronous Mirroring
IMPORTANT:The Business Continuity Clustering product does not perform data mirroring. You must separately configure either storage-based mirroring or host-based file system mirroring.
Storage-based synchronous mirroring is preferred and is provided by storage hardware manufacturers. For information about storage-based mirroring, consult your storage system vendor or see the storage system vendor documentation.
Host-based synchronous mirroring functionality is included with the Novell Storage Services NSS file system (NSS mirroring) that is part of OES. NSS mirroring is a checkpoint-based synchronous mirroring solution. Data blocks are written synchronously to multiple storage devices. It is an alternative to storage-based synchronous replication options.
IMPORTANT:NSS pool snapshot technology does not work in a business continuity cluster.