Management issues in storage area networks: detection and isolation of performance problems

This paper explores merging SAN performance management tools into the host system thus dissolving the traditional boundary between hosts and storage. The host service time distribution is exploited to locate caches in the SAN, detect and isolate contention in the communication channels and backend disk drives. We define essential metrics and measure I/O workloads over extended periods to define baseline behavior. We have implemented architecture to acquire configuration and performance data from agents on the host and SAN elements. In addition to performance management this data is the basis of management functions such as capacity planning, and sizing host and SAN resources required for application rollout and expansion. The static dependency map (SAN topology or 'wiring' diagram), provided by current SAN management tools, is extended into the host server. We then attempt to develop a corresponding dynamic dependency view showing how performance metrics at the application and host level, such as I/O queuing levels and service times, relate to response times in the SAN. The dynamic view is also an important complement to the static dependency graph because the actual traffic flow may be difficult to deduce from the topology.