FILE SYSTEM HAVING PREDICTABLE REAL-TIME PERFORMANCE

A file system that permits predictable accesses to file data stored on devices that may have a variable access latency dependent on the physical location of the file on the physical storage device. A variety of features that guarantee timely, real-time response to I/O file system requests that specify deadlines or other alternative required quality-of-service parameters. The file system addresses needs to accommodate the file systems of storage devices such as disks that have an access time dependant on the physical location of the data within the storage device. A two-phase, deadline-driven scheduler considers the impact of disk seek time on overall response times. Non real-time file operations may be preempted. Files may be preallocated to help avoid access delay caused by non-contiguity. Disk buffers may also be preallocated to improve real-time file system performance.