HP Certified: HP-UX System Administration

The Logical Volume Manager (LVM) approach is used to add flexibility to disk management tasks . In this chapter, you learned about disk devices and the ways of using disks for file systems. The whole-disk approach assigns the whole disk to a file system. The LVM approach introduces concepts of physical volumes, volume groups, and logical volumes. Physical volumes represent actual physical disks. Physical volumes are combined to create a volume group . Different logical volumes can then be created in a volume group. Information about LVM can be displayed with the help of the pvdisplay , vgdisplay , and lvdisplay commands. These commands show physical and logical extents that represent the smallest amount of disk space that can be allocated on a physical and logical volume.

The pvcreate command is used to create a physical volume. You may want to use the mediainit command to initialize physical media. After creating a physical volume, you can create volume groups and logical volumes with the help of the vgcreate and lvcreate commands. During the volume group creation process, the volume group directory and control file are created using the mkdir and mknod commands.

A file system is a structure for creating and storing files and directories. HP-UX supports many types of file systems. The most important of these are the High-Performance File system (HFS) and the Journaled File System (JFS). HFS is the traditional HP-UX file system and is mandatory for storing kernel files. JFS is a new and more-flexible file system. HP OnlineJFS (Advanced JFS) provides additional advantages over the base JFS file system as it can be maintained without unmounting. HFS is divided into blocks and fragments . A block is the minimum amount of data that is read in one cycle. A fragment is the minimum space that can be allocated to a file. JFS is an extent-based file system.

A new file system can be created using the newfs command. After creating a new file system, you need to mount it on a directory. This directory is called the mount point for that file system. File systems can be mounted automatically at boot time by putting them in the /etc/fstab file.

Space utilization on a file system is monitored using the bdf command. If you are running short of space on a file system, you can extend volume groups, logical volumes, and file systems with the help of the vgextend , lvextend , and extendfs commands, respectively. Before extending a file system, you need to unmount it. A file system can't be unmounted if some of its files are being used by running processes. The fuser command is used to terminate processes that are using files on a file system.

You can also use SAM to carry out all these operations on disks and file systems. A damaged file system can be repaired with the help of the fsck command.