Evaluation of active disks for decision support databases

Growth and usage trends for large decision support databases indicate that there is a need for architectures that scale the processing power as the dataset grows. To meet this need, several researchers have recently proposed Active Disk architectures which integrate substantial processing power and memory into disk units. In this paper, we evaluate Active Disks for decision support databases. First, we compare the performance of Active Disks with that of existing scalable server architectures: SMP-based conventional disk farms and commodity clusters of PCs. Second, we evaluate the impact of several design choices on the performance of Active Disks. We focus on the performance impact of interconnect bandwidth, amount of disk memory and disk-to-disk communication architecture on decision support workloads. Our results show that for identical disks, number of processors and I/O interconnect, Active Disks provide better price/performance than both SMP-based conventional disk farms and commodity clusters. Experiments evaluating the impact of design alternatives in Active Disk architectures indicate that: (1) for configurations up to 64 disks, a dual fibre channel arbitrated loop interconnect is sufficient even for the most communication-intensive decision support tasks; (2) most decision support tasks do not require a large amount of memory; and (3) direct disk-to-disk communication is necessary for achieving good performance on tasks that repartition all (or a large fraction of) their dataset.