A mechanism is provided in a data processing system for on-demand caching in a wide area network (WAN) separated distributed file system or clustered file system. The mechanism monitors file access by a plurality of cache sites in the WAN separated distributed file system or clustered file system. The mechanism identifies access patterns by cache sites. The mechanism shares the access patterns with the plurality of cache sites. A given cache site within the plurality of cache sites combines the access patterns with local access information and identifies files to pre-fetch based on the combined information.