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CHAPTER 5 File System Management

5.7 XFS (IRIX)

IRIX 6.2 includes the 64-bit journalled file system, XFS, as the default file system. It was included in IRIX 5.3 as an option, but EFS was the default file system for that release. It comes with a volume manager, xlv, and supports disk striping, concatenation of disk partitions, and mirroring. It supports CacheFS, AutoFS, and NFS version 3. With 64-bit addresses it will support files and file system of up to 1 TB, under IRIX 5.3 and 9 million TB under IRIX 6.2 for systems supporting 64-bit kernels. XFS does not support disk quotas.

XFS is a journalled file system. It logs changes to the inodes, directories and bitmaps to the disk before the original entries are updated. Should the system crash before the updates are done they can be recreated using the log and updated as intended.

XFS uses a space manager to allocate disk space for the file system and control the inodes. It uses a namespace manager to control allocation of directory files. These managers use B-tree indexing to store file location information, significantly decreasing the access time needed to retrieve file information.

Inodes are created as needed and are not restricted to a particular area on a disk partition. XFS tries to position the inodes close to the files and directories they reference. Very small files, such as symbolic links and some directories, are stored as part of the inode, to increase performance and save space. Large directories use B-tree indexing within the directory file to speed up directory searches, additions and deletions.

Unix System Administration - 8 AUG 1996
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