Storage Policies for a Two-Cache System

We study storage policies for a two-cache system where each request for a file arrives at one of the two caches. A request can be served by either one of the two caches or a central server. Serving a request using the cache at which it is received is the most preferred mode of service and is assumed to be free. The other cache can serve the request at a low, but non-zero cost, and the central server can serve it at a high cost. The aim is to design storage policies which minimize the cost of serving incoming requests. Via analysis and simulations, we compare the performance of the optimal caching policy with the locally optimal storage policy which makes decisions only based on the request arrival process at that particular cache.