Differences between JFS and Enhanced JFS

There are many differences between JFS and Enhanced JFS.

Function JFS Enhanced JFS
Optimization 32-bit kernel 64-bit kernel
Maximum file system size 32 terabyte 4 petabytes

Note: This is an architectural limit. AIX® currently only supports up to 16 terabytes.
Maximum file size 64 gigabytes 4 petabytes

Note: This is an architectural limit. AIX currently only supports up to 16 terabytes.
Number of I-nodes Fixed at file system creation Dynamic, limited by disk space
Large file support As mount option Default
Online defragmentation Yes Yes
namefs Yes Yes
Compression Yes No
Quotas Yes Yes
Deferred update Yes No
Direct I/O support Yes Yes


  • Cloning with a system backup with mksysb from a 64-bit enabled JFS2 system to a 32-bit system will not be successful.
  • Unlike the JFS file system, the JFS2 file system will not allow the link() API to be used on its binary type directory. This limitation may cause some applications that operate correctly on a JFS file system to fail on a JFS2 file system.
  • Journaling
    Before writing actual data, a journaling file system logs the metadata, thus incurring an overhead penalty that slows write throughput.
  • Directory organization
    An index node, or i-node, is a data structure that stores all file and directory properties. When a program looks up a file, it searches for the appropriate i-node by looking up a file name in a directory.
  • Scaling
    The main advantage of using Enhanced JFS over JFS is scaling.

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