A method for data storage includes encoding input data with an Error Correction Code (ECC), to produce encoded data. The encoded data is formatted in a super-frame consisting of a given number of burst sequences arranged in parallel, each burst sequence consisting of one or more bursts of multiple bytes of the encoded data. The burst sequences of the super-frame are stored in respective memory devices over a single data bus having a bus width, in bytes, that is equal to the given number.