Operating a RAID array with unequal stripes, the RAID array comprising N number of drives, where each RAID stripe includes P number of parity drives and N-P number of data drives, including buffering, by a RAID controller, write operations received from a host, each write operation specifying data to be written to the RAID array; distributing, by the RAID controller, the data to be written amongst N-P write groups, including: dividing the data into chunks of a sub-stripe size, wherein the sub-stripe size is less than a parity stripe size; and assigning the chunks, in round-robin order, to the N-P write groups; calculating parity from the N-P write groups; and writing the N-P write groups and the calculated parity as a first RAID stripe to the RAID array.