Systems, methods, and other embodiments associated with a distributed cache coherency protocol are described. According to one embodiment, a method includes receiving a request from a requester for access to one or more memory blocks in a block storage device that is shared by at least two physical computing machines and determining if a caching right to any of the one or more memory blocks has been granted to a different requester. If the caching right has not been granted to the different requester, access is granted to the one or more memory blocks to the requester.