A shared storage system is described herein that is based on an append-only model of updating a storage device to allow multiple computers to access storage with lighter-weight synchronization than traditional systems and to reduce wear on flash-based storage devices. Appending data allows multiple computers to write to the same storage device without interference and without synchronization between the computers. Computers can also safely read a written page without using synchronization because the system limits how data can be changed once written. The system may record a log of append operations performed and ensure idempotence by storing a key specified by the caller in the log along with each log entry. The system also provides broadcasts about appended data to computers so that coordination between computers can occur without direct communication between the computers.