Optimization of Mass Storage Hierarchies

Optimization is often a question of where one should put one’s money in improving performance. As far as large storage hierarchies go, intuition suggests (and common practice supports) adding as much as is affordable of the fastest technology available. Many cache hierarchy studies have shown that this is often not the optimal approach, and we show that for mass storage hierarchies it always tends to be the wrong approach. For large data sets, as is the case for network file servers, a machine with no RAM and several gigabytes of disk performs 30% faster than a machine with no disk and a cost-equivalent amount of RAM.