A fault tolerant hybrid memory structure and memory management algorithms

This paper proposes a cost effective fault tolerant memory structure. It uses the modified status of virtual memory pages as the basis to propose a system with two classes of memory. One class is for modified pages, and the other is for pages not modified. The term hybrid memory system is used to describe this system. Results show the cost savings for a hybrid system over a traditional fault tolerant system. Hybrid virtual memory algorithms are proposed for the system. The traditional lifetime and space-time measures of virtual memory algorithms are extended for the hybrid algorithms. This includes “cost-weighted” measures to reflect the fact that the two classes of memory may have different resource allocation constraints. A theoretical result is presented for the effect of combining the hybrid lifetime functions. Finally, a framework for developing hybrid algorithms is presented with experimental results illustrating the analysis. It is shown that the lifetime measure for the hybrid policies can show improvements over traditional algorithms