Methods of writing and recovering erasure coded data

摘要

An embodiment of a method of writing erasure coded data swaps a new data block for an old data block within a stripe of erasure coded data. The stripe of erasure coded data comprises data blocks and a redundancy block. The method computes a redundancy update parameter for the redundancy block using the new data block and the old data block. The method updates the redundancy block using the redundancy block, the redundancy update parameter, and a mathematical operator. An embodiment of a method of recovering erasure coded data obtains a lock on a subset of data blocks and one or more redundancy blocks. The method determines whether the subset of the data blocks and the one or more redundancy blocks includes sufficient blocks to restore the stripe. If not, the method relaxes the lock to allow at least one update of the one or more redundancy blocks while not allowing any writes of the data blocks. The method uses the subset to restore the stripe.