Red Hat GLOBAL FILE SYSTEM 5.0, Руководство администратора

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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 volumes to the volume group. For more information on extending a
striped volume, see Section 4.9, “Extending a Striped Volume” .
3.3. Mirrored Logical Volumes
A mirror maintains identical copies of data on different devices. When data is written to one
device, it is written to a second device as well, mirroring the data. This provides protection for
device failures. When one leg of a mirror fails, the logical volume becomes a linear volume and
can still be accessed.
LVM supports mirrored volumes. When you create a mirrored logical volume, LVM ensures that
data written to an underlying physical volume is mirrored onto a separate physical volume. With
LVM, you can create mirrored logical volumes with multiple mirrors.
An LVM mirror divides the device being copied into regions that are typically 512KB in size.
LVM maintains a small log which it uses to keep track of which regions are in sync with the
Mirrored Logical Volumes
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