On the effect of link failures in fibre channel storage area networks

The fast growth of data intensive applications has caused a change in the traditional storage model. The server-to-disk approach is being replaced by storage area networks (SANs), which enable storage to be externalized from servers, thus allowing storage devices to be shared among multiple servers. The prominent technology for implementing SANs is Fibre Channel, due to its suitability for storage networking. Although the probability of a link failure for individual links in a SAN is very low, this probability dramatically increases as the network size becomes larger. Moreover, there are external factors, such as accidental link disconnections, that also can affect the overall SAN reliability. Until the faulty element is replaced, the SAN is functioning in a degraded mode. In this paper we analyze by simulation the performance degradation of Fibre Channel storage area networks when failures in links occur, quantifying how much the global SAN performance is reduced during the time the system remains in the degraded state. We perform this analysis by using both synthetic and real I/O traffic. Simulation results show that performance degradation mainly depends on the routing algorithm and the switch architecture used.