Planning: MD3600f Series Storage Array Terms and Concepts 59Using Snapshot and Disk Copy TogetherYou can use the Snapshot Virtual Disk and Virtual Disk Copy premiumfeatures together to back up data on the same storage array, or to restore thedata on the snapshot virtual disk to its original source virtual disk.You can copy data from a virtual disk by:• Taking a point-in-time snapshot of the data (online)• Copying the data to another virtual disk using a virtual disk copy (offline)You can select a snapshot virtual disk as the source virtual disk for a virtualdisk copy. This configuration is one of the best ways you can apply thesnapshot virtual disk feature, since it enables complete backups without anyimpact on the storage array I/O.You cannot use a snapshot repository virtual disk as a source virtual disk or asa target virtual disk in a virtual disk copy. If you select the source virtual diskas the target virtual disk of a virtual disk copy, you must disable all snapshotvirtual disks associated with the source virtual disk.Multi-Path SoftwareMulti-path software (also referred to as the failover driver) is a softwareresident on the host server that provides management of the redundant datapath between the host server and the storage array.The multi-path software identifies the existence of multiple paths to a virtualdisk and establishes a preferred path to that disk. If any component in thepreferred path fails, the multi-path software automatically re-routes I/Orequests to the alternate path so that the storage array continues to operatewithout interruption.NOTE: Multi-path software is available on the MD3600f Series resource media.Preferred and Alternate Controllers and PathsA preferred controller is a RAID controller module designated as the owner ofa virtual disk or disk group. The preferred controller is automatically selectedby MDSM when a virtual disk is created. You can change the preferred RAIDcontroller module owner of a virtual disk after it is created. If a host is onlyconnected to only one RAID controller module, the preferred owner mustmanually be assigned to the RAID controller module the host can access.
