Operation Manual
partitions on a running system, LVM provides a virtual pool (volume group, VG for
short) of memory space from which logical volumes (LVs) can be created as needed.
The operating system accesses these LVs instead of the physical partitions. Volume
groups can occupy more than one disk, so that several disks or parts of them may con-
stitute one single VG. This way, LVM provides a kind of abstraction from the physical
disk space that allows its segmentation to be changed in a much easier and safer way
than with physical repartitioning. Background information regarding physical partitioning
can be found in Section 3.1.1, “Partition Types” (page 75) and Section 3.1, “Using the
YaST Partitioner” (page 73).
Figure 3.3:
Physical Partitioning versus LVM
Figure 3.3, “Physical Partitioning versus LVM” (page 85) compares physical partitioning
(left) with LVM segmentation (right). On the left side, one single disk has been divided
into three physical partitions (PART), each with a mount point (MP) assigned so that
the operating system can gain access. On the right side, two disks have been divided
into two and three physical partitions each. Two LVM volume groups (VG 1 and VG 2)
have been dened. VG 1 contains two partitions from DISK 1 and one from DISK 2.
VG 2 contains the remaining two partitions from DISK 2. In LVM, the physical disk
partitions that are incorporated in a volume group are called physical volumes (PVs).
Within the volume groups, four LVs (LV 1 through LV 4) have been dened. They
can be used by the operating system via the associated mount points. The border between
different LVs do not need to be aligned with any partition border. See the border between
LV 1 and LV 2 in this example.
LVM features:
• Several hard disks or partitions can be combined in a large logical volume.
•
Provided the conguration is suitable, an LV (such as /usr) can be enlarged if free
space is exhausted.
Advanced Disk Setup 85