Enabling efficient recovery from multiple failures together with one latent error in a storage array

An apparatus of managing a storage array consisting of a number (n) storage devices, the apparatus comprising:

• a striping unit configured to stripe the storage array to form a number (m) stripes, wherein each stripe contains the number (n) storage chunks from the number (n) storage devices respectively, and the storage array comprises a number (n*M) storage chunks;
• a selection unit configured to select a number (F) storage chunks from each stripe as local parity chunks, select a number (L) storage chunks from the storage array as global parity chunks, and use at least one of the storage chunks in the storage array except the local parity chunks and the global parity chunks as data chunks, wherein at least one of the storage devices in the storage array comprises one or more data chunks and one or more global parity chunks;
• a local parity storage unit configured to perform a number (F+L) fault tolerant erasure coding on data in all the data chunks in one of the number (m) stripes to generate the number (F+L) groups of parity data, and store only the number (F) groups of parity data therein respectively into number (F) local parity chunks in the one of the number (m) stripes;
• and
• a global parity storage unit configured to perform a cross-stripe operation on the number (L) groups of parity data of the number (F+L) groups of parity data to generate the number (L) groups of global parity data, and store the number (L) groups of global parity data respectively into the number (L) global parity chunks,
• wherein the number (F) is less than the number (n).