Lvm Logical Volumes; Linear Volumes - Red Hat ENTERPRISE LINUX 5 - LOGICAL VOLUME MANAGER ADMINISTRATION Manual

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LVM Logical Volumes

A logical volume is allocated into logical extents of the same size as the physical extents. The extent
size is thus the same for all logical volumes in the volume group. The volume group maps the logical
extents to physical extents.
2.3. LVM Logical Volumes
In LVM, a volume group is divided up into logical volumes. There are three types of LVM logical
volumes: linear volumes, striped volumes, and mirrored volumes. These are described in the following
sections.

2.3.1. Linear Volumes

A linear volume aggregates multiple physical volumes into one logical volume. For example, if you
have two 60GB disks, you can create a 120GB logical volume. The physical storage is concatenated.
Creating a linear volume assigns a range of physical extents to an area of a logical volume in order.
Figure 2.2, "Extent Mapping"
For example, as shown in
logical extents 1 to 99 could map to one
physical volume and logical extents 100 to 198 could map to a second physical volume. From the
point of view of the application, there is one device that is 198 extents in size.
Figure 2.2. Extent Mapping
Figure 2.3,
The physical volumes that make up a logical volume do not have to be the same size.
"Linear Volume with Unequal Physical Volumes"
shows volume group VG1 with a physical extent size
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