1. A method for writing metadata to a mass storage array comprising a plurality of mass storage devices, the array being divided into stripes having at least one block written to each of the mass storage devices, the method comprising: maintaining metadata relating to the array in a structure on the array; detecting a change to existing metadata stored in the structure; reading a parity block from a stripe of the array where changed metadata is to be stored in the structure; calculating a new parity for the stripe using only the existing metadata, the changed metadata, and the parity read from the array; storing the changed metadata in the structure on the array; and storing the new parity in the structure on the array.