Although the cost of storage has fallen considerably in recent years, at the same time the need for storage has risen immensely, so that we can observe of a real data explosion. The administrative costs associated with these quantities of data should not, however, increase to the same degree. The introduction of storage networks is a first step towards remedying the disadvantages of the server-centric IT architecture (Section 1.1). Whereas in smaller environments the use of storage networks is completely adequate for the mastery of data, practical experience has shown that, in large environments, a storage network alone is not sufficient to efficiently manage the ever-increasing volumes of data.
In this chapter we will introduce the storage virtualisation in the storage network, an approach that simplifies the management of large quantities of data. The basic idea behind storage virtualisation is to move the storage virtualisation functions from the servers (volume manager, file systems) and disk subsystems (caching, RAID, instant copy, remote mirroring, LUN masking) into the storage network (Figure 5.1). This creates a new virtualisation entity which, as a result of its positioning in the storage network, spans all servers and storage systems. This new virtualisation in the storage network permits the full utilisation of the potential of a storage network with regard to the efficient use of resources and data, the improvement of performance and protection ...