The Continuous Media File System, CMFS, supports real-time storage and retrieval of continuous media data (digital audio and video) on disk. CMFS clients read or write files in "sessions", each with a guaranteed minimum data rate. Several sessions can exist concurrently, sharing a single disk drive. Clients can concurrently access non-real-time files on the same disk. CMFS addresses several interrelated design issues: 1) real-time semantics of sessions; 2) disk layout; 3) acceptance test for new sessions, and 4) disk scheduling policy. We use simulation to compare different design choices and to estimate the performance of CMFS under various load conditions and hardware assumptions.