Reader-writer Locks for Network Attached Storage and Storage Area Network S 1

Network Attached Storage and Storage Area Networks are emerging as the technology of choice for large-scale data storage. A key feature of such storage devices is that they can be directly accessed by applications without the intervention of le servers. Hence, issues such as data-sharing and security cannot be handled by le-servers. This paper addresses the issue of data-sharing by presenting a Reader-Writer locking mechanism that is controlled by the storage devices. The Reader-Writer synchronization refers to the classical problem of shared reader access and exclusive writer access to shared data. The proposed mechanism requires a simple data structure per data-item to be maintained at the devices and client nodes. Since requests are issued across the network, all locks are based on blocking. The algorithm presented here is scalable and fault-tolerant.