The purpose of this chapter is to convey the basic idea underlying this book. To this end we will first describe conventional server-centric IT architecture and sketch out its limitations (Section 1.1). We will then introduce the alternative approach of storage-centric IT architecture (Section 1.2), explaining its advantages using the case study ‘Replacing a Server with Storage Networks’ (Section 1.3). Finally, we explain the structure of the entire book and discuss which subjects are not covered (Section 1.4).
1.1 SERVER-CENTRIC IT ARCHITECTURE AND ITS LIMITATIONS
In conventional IT architectures, storage devices are normally only connected to a single server (Figure 1.1). To increase fault tolerance, storage devices are sometimes connected to two servers, with only one server actually able to use the storage device at any one time. In both cases, the storage device exists only in relation to the server to which it is connected. Other servers cannot directly access the data; they always have to go through the server that is connected to the storage device. This conventional IT architecture is therefore called server-centric IT architecture. In this approach, servers and storage devices are generally connected together by SCSI cables.
As mentioned above, in conventional server-centric IT architecture storage devices exist only in relation to the one or two servers to which they are connected. The failure of both of these computers would make it impossible to access ...