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For details about how to view file system properties, see “Viewing File System Properties of an AIX Journaling File System”.

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(1) A file system is a collection of files, directories, and other data structures that record the location of directories and files. A file system is created on a logical volume. All directories and files of the file system are stored in this logical volume. Therefore, the size of the file system cannot exceed the size of the logical volume. (2) The installation of a non-root file system refers to linking the root of a file system to a specific empty directory so that users can access any directory and files in the file system through this empty directory. This empty directory is called Mount Point. A file system can only be used by users through installation. (3) AIX systems support five types of file systems: JFS, JFS2, NFS, CDRFS and UDFS. (4) When AIX is installed, there are seven journalistic file systems in rootvg, The values are root file system (/dev/hd4), /proc file system, /usr file system (/dev/hd2), /var file system (/dev/hd9var), /home file system (/dev/hd1), and/TMP File system (/dev/hd3) and /opt file system (/dev/hd10opt). (5) AIX 5L supports /proc file systems. This pseudo-file system maps process and kernel data structures with corresponding files. In the /proc file system, each subdirectory is a process and the directory name is the process number (PID). (6) Before creating a log file system, set the following parameters: Number of I-Nodes, size of Allocation Group, size of Fragment, size of log of log file system, and size of file system. (7) Journalistic file systems are built on Logical volumes, which are divided into many fixed-size units called Logical blocks. Logical blocks are typically 4 096 bytes in size. (8) The super block stores information about the entire file system, such as the size of the file system, the number of data blocks contained in the file system, the status of the file system, and the size of the allocation group. (9) Fragmentation is the smallest unit of disk space allocated by a file system and can be less than 4,096 bytes. If the logical chunk is divided into multiple shards, storing data in shards of less than 4,096 bytes is a more efficient use of disk space, thus reducing disk space waste. (10) The number of I-nodes in a file system limits the number of files and the size of the file system. A log file system has an NBPI (Number of Bytes Per i-node) parameter, which affects the Number of I-nodes in the file system. (11) A journalized file system divides its space into many Allocation groups (AGS). Each Allocation Group contains I nodes and data blocks. In this way, I nodes and data blocks can be distributed in the entire file system. Make the I node physically as close as possible to the data block it points to to improve disk access performance. (12) AIX uses a special logical volume to record file system changes to meta-data. This special logical volume is called JFS Logging Device. All transactions (metadata) generated in the file system structure are logged to a JFS logging logical volume. The JFS log logical volume is a circular log table. This transaction log is used to recover the file system in the event of an abnormal system outage. (13) Each file has a corresponding I node to store its control information and location information of data blocks. Essentially, an I node is a pointer to a block of file data. (14) In AIX, there are two types of file I-nodes: static Disk I-nodes and dynamic in-core I-nodes. The disk I nodes are stored on disk, and the kernel I nodes are located in the kernel area of the system, the JFS cache. (15) All information about the File system is stored in the /etc/filesystems File. The /etc/vfs File describes the types of Virtual File Systems (VFS) that have been installed in the system. The main contents include the type name, type code, and file system helper. (16) the LSFS command lists the various filesystems defined in the system. It obtains information from /etc/filesystems files and volume groups and displays it in a format that is easily acceptable to users. The mount command without any parameters can display the installed file systems in the current system. Run the df command to check the space usage of the file system. The du command displays the size of a directory or file. To mount a file system, use the mount command. To unmount a previously installed file system, use the umount command. The command to delete a file system is RMFS, and the command to modify the properties of a file system is CHFS. (18) Run the FSCK command to check the consistency of the file system and repair the damaged file system. \