File System Administration

 

Journaled file System

Two type supported by AIX

• JFS    : Journaled File System
• JFS2  : Enhanced JFS

Journaling :

•  Before writing the actual data, a journaling file system logs the metadata to a circular JFS log on disk.
• In the event of an OS crash, journaling retores consistencu by processing the information in the JFS log file.

JFS

• Original AIX file system
• Developed for transaction-oriented, high performance Power system
• Both scaleable and robust
• Logging feature available.
• Its recoverable file system which means that even if the system crash, no fle system transaction will be  in an inconsistence state.

JFS2

• Default file system on AIX since version 5.3
• Filesystem can be dynamically increased and decreased.
• Data encryption
• Both internal and external  logging available
• Support Snapshot.
• Support for larger enable filesystem
• Minium Size of JFS2 file is 16MB

Steps involve in making FS

• Create a file system on volume group using crfs command
• mount it on directory   ( In order to activate that file system)

***  Each time we do any FS command, an entry is made in /etc/filesystems file

Command related to File system

Most important file system :  /etc/filesystems

• Creating a JFS2 file system : 

• The crfs creates a file system on a logical volume within a previously created volume group. We can also use smit crfs_j2  for same operation.
• A new logical volume is created for the filessystem and a entry is made into /etc/filesystems. 
• The Options include:
• -v   : Filesystem type ( Example: jfs2)
• -m  : mount point
• -A  : mount automatically on reboot or not
• -p   : Mount as ro/rw
• -l    : size of log volume in case of jfs
• -g   : volume group name
• -d   : logical volume group name
• -a   : size of file system

 

• Example:  Creating a file system without mentioning a Logical Volume name

• crfs -v jfs2  -g  rootvg  -a size=16M  -m  /data

                         

By default a logical volume name : fslv02 is created

We have to mount the FS over the mount point in order to user the FS

 

• Example:  Creating a file system by mentioning a logical volume name
• crfs -v jfs2 -d datalv1 -a size=20M  -m  /data



• Changing the size of File system:

•  We can increase (+), decrease(-) the size of File system by using chfs command with -a size options
• The minium size you can decrease by is 16M

                               chfs -a size=* 

• Example: Increaing the File System :   chfs -a size=+21M /data 

• Example:  Decreaing the size of file sytem :  chfs -a size=-128M /data





• Removing the JFS2 file system

• The file system must first be unmounted.
• We can remove the FS  by using smitty rmfs2   or   rmfs
• Options for rmfs command are :
• -r    : Remove the mountpoint of the system
• -i    : Display warning and prompt the user to remove the file system