There is disclosed a technique for use in optimizing write operations for flash devices. A system having a plurality of flash based solid state drives receives a write request to overwrite existing data stored on the solid state drives with new data. The write request data is formatted using a write granularity having a first size and the solid state drives are configured with a write granularity having a second size. Corresponding existing data is retrieved. The new data and the existing data are subdivided into multiple corresponding subunits where each subunit has a size equal to the second size. Each new data subunit is compared with each corresponding existing data subunit to identify which new data subunits include modified data. The new data subunits identified as having modified data are written to corresponding locations on the solid state drives.