Red Hat GLOBAL FILE SYSTEM 5.0, Administrator'S Manual

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In the Linux kernel (and throughout this document), sectors are considered to be
512 bytes in size.
Figure 2.1. Physical Volume layout
1.2. Multiple Partitions on a Disk
LVM allows you to create physical volumes out of disk partitions. It is generally recommended
that you create a single partition that covers the whole disk to label as an LVM physical volume
for the following reasons:
• Administrative convenience
It is easier to keep track of the hardware in a system if each real disk only appears once. This
becomes particularly true if a disk fails. In addition, multiple physical volumes on a single disk
may cause a kernel warning about unknown partition types at boot-up.
• Striping performance
LVM can not tell that two physical volumes are on the same physical disk. If you create a
striped logical volume when two physical volumes are on the same physical disk, the stripes
could be on different partitions on the same disk. This would result in a decrease in
performance rather than an increase.
Although it it is not recommended, there may be specific circumstances when you will need to
divide a disk into separate LVM physical volumes. For example, on a system with few disks it
Chapter 2. LVM Components
8