JFS and JFS2 functions
Enhanced Journaled File System (JFS2) is a file system that provides the capability to store much larger files than the existing Journaled File System (JFS).
You can choose to implement either JFS or JFS2. JFS2 is the default
file system in AIX® 6.1.
Note: Unlike
the JFS file system, the JFS2 file system will not allow the link() API
to be used on files of type directory. This limitation may cause some
applications that operate correctly on a JFS file system to fail on
a JFS2 file system.
The following table provides a summary of JFS and JFS2 functions:
| Functions | JFS2 | JFS |
|---|---|---|
| Fragments and block size | Block sizes (bytes): 512, 1024, 2048, 4096 Maximum file system size in terabytes (TBs): 4, 8, 16, 32 |
Fragment sizes (bytes): 512, 1024, 2048, 4096 Maximum file system size in gigabytes (GBs): 128, 256, 512, 1024 |
| Maximum file system size | 32 TBs | 1 TB |
| Minimum file system size | 16 MBs | Not Applicable |
| Maximum file size | 16 TBs | Approximately 63.876 GBs |
| Number of i-nodes | Dynamic, limited by disk space | Fixed, set at file system creation |
| Directory organization | B-tree | Linear |
| Compression | No | Yes |
| Quotas | Yes | Yes |
| Error logging | Yes | Yes |
Note:
- The maximum file size and maximum file system size is limited to (1 TB - (physical partition size)) when used with the 32-bit kernel. For example, if the physical partition size for the volume group is 64 MB, then the maximum file system size is (1 TB - 64 MB) = (1048576 MB - 64 MB) = 1048512 MB. This is due to an underlying limitation on the maximum size of a logical volume when using the 32-bit kernel.
- JFS2 supports the standard AIX error logging scheme. For more information on AIX error logging, please see Error-Logging Overview in General Programming Concepts: Writing and Debugging Programs.