Methods and systems for preventing permanent data loss due to a single failure in an array of storage devices are described. In particular, a defective memory block is detected and data that was on the now defective memory block is reconstructed using backup data in the array. The reconstructed data is stored in a replacement memory block, without requiring the rewriting of data in non-defective memory blocks. The information mapping the defective memory block to the replacement memory block may be stored as metadata on a storage device.