JFS (file system)
Journaled File System (JFS) is a 64-bit journaling file system created by IBM. There are versions for AIX, OS/2, eComStation, ArcaOS and Linux operating systems. The latter is available as free software under the terms of the GNU General Public License (GPL). HP-UX has another, different filesystem named JFS that is actually an OEM version of Veritas Software's VxFS.
| Developer(s) | IBM et al. |
|---|---|
| Full name | IBM Journaled File System |
| Introduced | 1990 and 1999 with JFS1 in AIX 3.1 and JFS in OS/2 4.5 |
| Partition IDs | 0x35 (MBR) |
| Structures | |
| Directory contents | B+ tree |
| File allocation | Bitmap/extents |
| Limits | |
| Max volume size | 32 × 250 bytes (32 PiB) |
| Max file size | 4 × 250 bytes (4 PiB) |
| Max no. of files | No limit defined |
| Max filename length | 255 bytes |
| Allowed filename characters | Any Unicode except NUL |
| Features | |
| Dates recorded | Modification (mtime), attribute modification (ctime), access (atime) |
| Date resolution | 1 ns |
| Forks | Yes |
| File system permissions | Unix permissions, ACLs |
| Transparent compression | Only in JFS1 on AIX |
| Transparent encryption | No (provided at the block device level) |
| Data deduplication | No |
| Other | |
| Supported operating systems | AIX, OS/2, Linux, eComStation, ArcaOS |
In the AIX operating system, two generations of JFS exist, which are called JFS (JFS1) and JFS2 respectively.
IBM's JFS was originally designed for 32-bit systems. JFS2 was designed for 64-bit systems.
In other operating systems, such as OS/2 and Linux, only the second generation exists and is called simply JFS. This should not be confused with JFS in AIX that actually refers to JFS1.