The storage manager, called LFS, uses the concepts of log-structured file systems[1] to increase the performance of the UNIX file system. In a log-structured file system, all modifications to the file system including data, directories, and metadata blocks are written to disk in large, sequential transfers that proceed at maximum disk bandwidth. Small file creation and deletion in LFS cause disk accesses that are large, sequential, and asynchronous. The log-structure of LFS requires that large disk regions be available for writing. LFS manages these regions by partitioning the disk into large sequential pieces called segments. Blocks are added to the file system a segment at a time and disjoint segments are linked together to form a logically consecutive segmented log. In order to keep segments available for writing, LFS performs an operation called segment cleaning. The operation reads fragmented segments into memory, compacts the live data, and writes it back to segments on disk. . . An LFS file system must manage the disk free space to keep open large regions of consecutive disk sectors. LFS simplifies this task by dividing the disk storage into large fixed-size pieces called segments 4.3.1. Segment summary blocks Each LFS segment contains a few sectors of summary information that identify the contents of the segment and allow segments to be formed into a linked list. The information is kept in a region of the segment called the summary block. The append only log abstraction can be visualized by following the links between segments.