Red Hat GLOBAL FILE SYSTEM 5.0, Руководство администратора

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The LVM Logical Volume Manager
This chapter provides a high-level overview of the components of the Logical Volume Manager
(LVM).
1. 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 will 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.
• Convenient device naming
Logical storage volumes can be managed in user-defined groups, which you can name
according to your convenience.
• Disk striping
You can create a logical volume that stripes data across two or more disks. This can
dramatically increase throughput.
• Mirroring volumes
Logical volumes provide a convenient way to configure a mirror for your data.
• Volume Snapshots
Chapter 1.
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