Stands for "Journaled File System." JFS is a 64-bit file system created by IBM. The initial version of JFS (also called JFS1) was developed for IBM's AIX operating system and was released in 1990. In 2001, IBM released JFS2 (the Enhanced Journaled File System), as well as a version of JFS that is compatible with the Linux operating system.
The "journaled" aspect of JFS means that the file system keeps tracks of changes to files and folders in a log file (or journal). This log can be used to backtrack certain changes in case of an unexpected power failure or system crash, which may prevent data corruption. For example, if a file is in the process of being moved or deleted when a computer crashes, the journal can be used to restore the file to its last stable state. Without the journal, the file may be truncated, which would make it unreadable and could produce other file system errors.
The Enhanced Journaled File System (JFS2) is similar to JFS, but supports much larger volumes and file sizes. For example, a hard disk formatted using JFS can be a maximum of one terabyte (TB) in size, while a JFS2-formatted disk can be up to 32 TB. JFS's maximum file size is slightly less than 64 gigabytes (GB), while JFS2 supports file sizes up to 16 TB. This large file capacity is especially important for storing large databases, which are often contained in a single file.
NOTE: JFS2 is supported by AIX 5.1 and later. It is also supported on Linux systems that have the "jfsutils" package installed.