So if you have an organisation wide storage which may be spread across network servers or multiple storage devices like tapes, opical, Sata et al then if you want to make it easier for users to use it then it is better to go for Storage Virtualisation. IN this the actual details of the storage device and physical location as well as the type of storage can be hidden from the user. One advantage could be that ordinary users can carry out complicated ack up and recovery operations and the method is highly user friendly.
The storage is given an abstraction. There are hardware and software devices to attain storage virtualisation. If you use hardware devices for packet switching its prone to evasdropping and if you use software controllers then the systems are inoperable with other vendors devices.
Storage abstraction can be used for cost savings in case of consolidation of infrastructure post M & A.