Scaling

The main advantage of using Enhanced JFS over JFS is scaling.

Enhanced JFS provides the capability to store much larger files than the existing JFS. The maximum size of a file under JFS is 64 gigabytes. Under Enhanced JFS, AIX currently supports files up to 16 terabytes in size, although the file system architecture is set up to eventually handle file sizes of up to 4 petabytes.

Another scaling issue relates to accessing a large number of files. The following illustration demonstrates how Enhanced JFS can improve performance for this type of access.

The above example consists of creating, deleting, and searching directories with unique, 10-byte file names. The results show that creating and deleting files is much faster under Enhanced JFS than under JFS. Performance for searches was approximately the same for both file system types.

The example below shows how results for create, delete, and search operations are generally much faster on Enhanced JFS than on JFS when using non-unique file names. In this example, file names were chosen to have the same first 64-bytes appended by 10-byte unique names. The following illustration shows the results of this test:

On a related note, caching of long (greater than 32 characters) file names is supported in both the JFS and Enhanced JFS name caches. This improves the performance of directory operations, such as the ls and find commands, on directories with numerous long file name entries.