Large scale high performance file proxy caching sites may be configured to coalesce many client write operations into one very large assemblage of modified file data. At some point the caching site will flush all modified file data downstream towards the origin file server. In some instances the amount of modified data being flushed may be more than can be transferred in a single network request. When multiple network requests are required, the consistency guarantee provided by many filesystems requires that the file either be updated with the data contained in all of the network requests or not be modified at all. In addition, once the first flush request is processed no other file read or write requests can be serviced until the last flush request has been processed. This document discloses methods for performing atomic multi-request flush operations within a large geographically distributed filesystem environment.