A shared disk implementation on distributed storage requires consistent behavior of disk operations. Deterministic consensus on such behavior is impossible when even a single storage node can fail. Atomic registers show how consistency can be achieved without reaching consensus, but suffer from a crash consistency problem. The presented shared disk algorithm, based on atomic registers and probabilistic consensus, can survive multiple storage node failures, as long as a majority of nodes respond. Categories and Subject Descriptors: D.4.5 [Operating Systems]: Reliability – fault-tolerance, verification; H.3.4 [Information Storage and Retrieval]: Systems and Software – distributed systems. General Terms: Algorithms, Reliability, Verification.