An apparatus for processing data includes a decoder configured to iteratively decode codewords in a data block representing a number of user data sectors, the codewords including user data, folded parity sector data and error correction code parity bits. The folded parity sector data includes a number of parity checks, each with multiple user data bits from each of the data sectors, and with an offset between each of the user data bits from the data sectors determined at least in part by a number of folds in the data sectors. The apparatus also includes a scheduler configured to control decoding of the codewords based at least in part on the folded parity sector data.