File system with read / write memory and a single read - and repeated read - memory

摘要

A file system (101) which has component file systems including a primary file system (111) which is read/write and a number of dump file systems (109) which are read only. Each dump file system is created from the primary file system by means of a dump operation and conserves the state of the primary file system at the time the dump operation was performed. Component file systems share read only storage elements (519) with older component file systems. The file system is implemented on a system including a file server (503), a magnetic disk mass storage device (507), and an optical write once-read many (WORM) disk (511 ). The magnetic disk mass storage device contains the read/write storage elements of the primary file system and encached read only storage elements from the WORM disk. Space (516) is reserved on the unwritten portion (515) of the WORM disk for the read-write storage elements of the primary file system. Techniques for performing file operations including opening, reading, writing, creating, and deleting files are disclosed, as well as techniques for performing the operations of dumping and restoring the primary file system.