FFS: Disk Awareness Is The Solution
Understand how the Fast File System (FFS) optimizes file storage by using disk-aware structures such as cylinder groups to improve performance and reliability. Learn about FFS's internal organization, including how it manages inodes, data blocks, and free space allocation, enhancing your knowledge of modern file system design.
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A group at Berkeley decided to build a better, faster file system, which they cleverly called the Fast File System (FFS). The idea was to design the file system structures and allocation policies to be “disk aware” and thus improve performance, which is exactly what they did. FFS thus ushered in a new era of file system research; by keeping the same interface to the file system (the same APIs, including open(), read(), write(), close(), and other file system calls) but changing the internal implementation, the authors paved the path for new file system construction, work that continues today. Virtually all modern file systems adhere to the existing interface (and thus preserve compatibility with applications) while changing their internals for performance, reliability, or other reasons.
Organizing structure: the cylinder group
The first step was to change the on-disk structures. FFS divides the disk into a number of cylinder groups. A single cylinder is a set of tracks on different surfaces of a hard drive that are the same distance ...