Method and apparatus for managing data in a distributed data storage system. In some embodiments, a plurality of storage devices define an overall available memory space. A control circuit stores a first copy of user data from a selected distributed data set in a working set of memory buffers, stores a duplicate, second copy of the user data in an alias set of memory buffers, generates parity data based on the second copy of the user data in the alias set of the memory buffers, and flushes the user data and the parity data from the alias set of memory buffers to the storage devices while the first copy of the user data remains in the working set of the memory buffers. In this way, subsequently received access commands can be serviced using the working set of the memory buffers.