A storage server is configured to receive a request to store a data block from a client. The request to store the data block is serviced by the storage server by compressing the data block into a compression group, which includes a number of compressed data blocks. The storage server stores the compression group in a non-volatile memory and flushes the compression group from the non-volatile memory to a physical storage device in response to reaching a consistency point. By compressing data to be stored in system memory of a storage server, the amount of data that can be processed during a given time period by a data storage system is increased. Furthermore, an increase in performance can be achieved at a lower cost, since the cost of additional physical system memory modules can be avoided.