Managing Systems and Workgroups: A Guide for HP-UX System Administrators

Planning a Workgroup
Setting Disk-Management Strategy
Chapter 2 81
“Whole Disk”
The alternative to LVM is “whole-disk” management, which as the name
implies treats the disk as a single unit.
Should You Use a Logical Volume Manager or “Whole Disk”?
Advantages of a logical volume manager:
• Logical volumes can span multiple disks:
— File systems (and individual files) can be larger than a single
physical disk.
— A logical volume can be as small or large as the file system
mounted to it requires.
— Space need not be wasted: small chunks of unused space from
several disks can be combined to create a usable volume.
• You can extend a file system without rebuilding it.
— Reducing a file system is more complex, but is also relatively
painless.
• LVM supports “Disk Mirroring” on page 82 and “Disk Striping” on
page 82.
Disadvantage of LVM:
• Complexity.
LVM is a sophisticated tool; as such, it takes time to learn, it requires
maintenance (configuration information needs to be backed up) and
things can go wrong (if configuration information is lost or corrupted,
there may be no way to get to the actual data on the disk, even
though this data may itself be intact).
But, your LVM configuration is automatically backed up every time
you change it (in /etc/lvmconf), and “Disk Mirroring” on page 82
provides insurance against data loss that is not available under the
“whole-disk” method.
You should certainly use LVM on file and application servers; on
workstations that have only a single disk, used only to store the
operating system and for swap, LVM is not necessary, though you may
choose to implement it anyway for the sake of uniformity, or because you
expect to add more disks to some workstations over time.