1. A method comprising: caching write requests directed to a backing store, the write requests for storing respective write data on the backing store, wherein caching a write request comprises: caching write data corresponding to the write request within a first cache storage, the write data designated to be written to the backing store from the first cache storage; and storing a redundant copy of the write data cached within the first cache storage on a second, persistent cache storage, separate from the first cache storage, wherein storing the redundant copy of the write data comprises recording a log entry comprising the write data in an ordered sequence of log entries on the second, persistent cache storage, each log entry corresponding to a set of write requests directed to the backing store; and maintaining associations between the write data cached within the first cache storage and log entries comprising redundant copies of the write data stored on the second, persistent cache storage.