HCSA: A Hybrid Client-Server Architecture

The HCSA (Hybrid Client-Server Architecture), a flexible system layout that combines the advantages of the traditional Client-Server Architecture (CSA) with those of the Shared Disk Architecture (SDA), is introduced. In HCSA, the traditional CSA-style I/O subsystem is modified to give the clients network access to both the server and the server's set of disks. Hence, the HCSA is more fault-tolerant than the CSA since there are two paths between any client and the shared data. Moreover, a simulation study demonstrates that the HCSA is able to support a larger number of clients than the CSA under similar system workloads. Finally, the HCSA can run applications in either a CSA mode, an SDA mode, or a combination of the two, thus offering backward compatibility with a large number of existing applications.