File System Types：


AIX supports multiple file system types. These include the following:

Journaled File System (JFS) or Enhanced Journaled File System (JFS2)
Network File System (NFS)
CD-ROM File System (CDRFS)
DVD-ROM File System (UDFS)
Journaled File System (JFS) or Enhanced Journaled File System (JFS2)
Supports the entire set of file system semantics. These file systems use database journaling techniques to maintain structural consistency. This prevents damage to the file system when the system is halted abnormally.

Each JFS or JFS2 resides on a separate logical volume. The operating system mounts the file system during initialization. This multiple file system configuration is useful for system management functions such as backup, restore, and repair, because it isolates a part of the file tree so that you can work on it.

A difference between JFS and JFS2 is that JFS2 is designed to support large files and large file systems. These file system types are described more thoroughly in Understanding JFS and JFS2.

Network File System (NFS)
Is a distributed file system that allows users to access files and directories located on remote computers and use those files and directories as if they were local. For example, users can use operating system commands to create, remove, read, write, and set file attributes for remote files and directories. NFS is described more thoroughly in the AIX 5L Version 5.2 Security Guide.

CD-ROM File System (CDRFS)
Allows access to the contents of a CD-ROM through the normal file system interfaces. CDRFS is described more thoroughly in Understanding CDRFS.

DVD-ROM File System (UDFS)
Allows access to the contents of a DVD through the normal file system interfaces. UDFS is described more thoroughly in Understanding UDFS.

Understanding JFS and JFS2
The journaled file system (JFS) and the enhanced journaled file system (JFS2) are built into the base operating system. Both file system types link their file and directory data to the structure used by the AIX Logical Volume Manager for storage and retrieval. A difference is that JFS2 is designed to accommodate a 64-bit kernel and larger files.

The following sections describe these file systems. Unless otherwise noted, the following sections apply equally to JFS and JFS2.

JFS2
JFS2 (enhanced journaled file system) is a file system, introduced in AIX 5L for POWER Version 5.1, that provides the capability to store m