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Chapter 1.
The LVM Logical Volume Manager
This chapter provides a high-level overview of the components of the Logical Volume Manager
(LVM), and includes a summary of new and changed LVM features in Red Hat Enterprise Linux
4.5.
1. New and Changed Features
This section lists new and changed features included with the initial release of Red Hat
Enterprise Linux 4.5.
• Red Hat Enterprise Linux 4.5 supports mirrored logical volumes in a cluster. For information
on creating and modifying mirrors, see
• Documentation for Red Hat Cluster Suite for Red Hat Enterprise Linux 4.5 has been
expanded and reorganized. For information on the available documents, see
"Related
Documentation".
2. Logical Volumes
Volume management creates a layer of abstraction over physical storage, allowing you to
create logical storage volumes. This provides much greater flexibility in a number of ways than
using physical storage directly.
A logical volume provides storage virtualization. With a logical volume, you are not restricted to
physical disk sizes. In addition, the hardware storage configuration is hidden from the software
so it can be resized and moved without stopping applications or unmounting file systems. This
can reduce operational costs.
Logical volumes provide the following advantages over using physical storage directly:
• Flexible capacity
When using logical volumes, file systems can extend across multiple disks, since you can
aggregate disks and partitions into a single logical volume.
• Resizeable storage pools
You can extend logical volumes or reduce logical volumes in size with simple software
commands, without reformatting and repartitioning the underlying disk devices.
• Online data relocation
To deploy newer, faster, or more resilient storage subsystems, you can move data while your
system is active. Data can be rearranged on disks while the disks are in use. For example,
you can empty a hot-swappable disk before removing it.
Section 4.1.3, "Creating Mirrored
Volumes".
Section 3,
1
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