Embodiments described herein include a PSL engine that includes various memory elements that permit the engine to grant locks on particular portions of data in a stripe in a RAID storage system. The PSL engine can assign (or lock) different blocks of the stripe for different operations. The PSL engine can grant locks to multiple operations for the same stripe if the operations access mutually exclusive blocks of the stripe. Each time a new operation is requested, the PSL engine determines whether the operation would affect a stripe data block that is currently assigned to another operation. If the new operation corresponds to a block of data in the stripe that includes data locked by another operation, the PSL engine assigns the new operation to a wait list. In one embodiment, the PSL engine maintains a wait list for each of the stripes in the RAID system.