METHOD AND SYSTEM FOR-CACHING REMOTE FILES LOCALLY FIELD OF THE INVENTION The invention relates generally to computers, and more particularly to file systems. BACKGROUND A set of content servers in a datacenter, e.g., a server farm, may serve content to many clients at various locations. Previously, the total set of content hosted by a given server farm was relatively small and could be transmitted to and stored on each of the content servers in the farm without excessive costs. Now, however, the amount of content available from a server farm is often in excess of several hundred gigabytes. Buying large capacity hard drives for servers, provisioning, them with all the content of a datacenter, and keeping the content on them up-to-date so that they can serve any content requested is expensive both in storage and transmission costs. This is particularly true when more than one datacenter is used to serve the content. What is needed is a method and system of effectively caching remote data locally such that the entirety of the content set can be st