Red Hat ENTERPRISE LINUX 5 - LOGICAL VOLUME MANAGER ADMINISTRATION Manual page 23

Striped Logical Volumes
striped logical volume. For large sequential reads and writes, this can improve the efficiency of the
data I/O.
Striping enhances performance by writing data to a predetermined number of physical volumes in
round-round fashion. With striping, I/O can be done in parallel. In some situations, this can result in
near-linear performance gain for each additional physical volume in the stripe.
The following illustration shows data being striped across three physical volumes. In this figure:
• the first stripe of data is written to PV1
• the second stripe of data is written to PV2
• the third stripe of data is written to PV3
• the fourth stripe of data is written to PV1
In a striped logical volume, the size of the stripe cannnot exceed the size of an extent.
Figure 2.5. Striping Data Across Three PVs
Striped logical volumes can be extended by concatenating another set of devices onto the end of the
first set. In order extend a striped logical volume, however, there must be enough free space on the
underlying physical volumes that make up the volume group to support the stripe. For example, if you
have a two-way stripe that uses up an entire volume group, adding a single physical volume to the
volume group will not enable you to extend the stripe. Instead, you must add at least two physical
Section 4.4.9,
volumes to the volume group. For more information on extending a striped volume, see
"Extending a Striped Volume".
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