JFS (Journaled File System)


JFS is a 64-bit file system that IBM has created. JFS has a full-form “Journaled File System.” 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) and a version of JFS compatible with the Linux operating system.

The “journaled” aspect of JFS means such a file system takes care of the tracks to see what changes have taken place in a log file (or journal) in files and folders.

This log is used to backtrack some changes if an unexpected power failure or system crash occurs in a case, which prevents data from being corrupted.

For example, if a file is in a process such as a move or deletes when a computer crashes, that journal is used to restore the file to its last stable state.

In the absence of a journal, the file can be truncated, which makes it unreadable and also causes other file system errors.

These Enhanced Journaled File System (JFS2) are similar to JFS, but they support larger volumes and file sizes.

For example, if a hard disk is formatted with JFS, it can be up to the size of a maximum of one terabyte (TB), whereas 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 very important for storing large databases often contained in a single file.

Note: JFS2 supports AIX 5.1 and above. It is supported in Linux systems with the “jfsutils” package installed.


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