Installation guide

Chapter 1. The LVM Logical Volume Manager

• You can now create a mirror log for a mirrored logical device that is itself mirrored by using the --

mirrorlog mirrored argument of the lvcreate command when creating a mirrored logical

device. For information on using this option, see Section 4.4.3, “Creating Mirrored Volumes”.

1.1.2. New and Changed Features for Red Hat Enterprise Linux 6.1

Red Hat Enterprise Linux 6.1 includes the following documentation and feature updates and changes.

• The Red Hat Enterprise Linux 6.1 release supports the creation of snapshot logical volumes of

mirrored logical volumes. You create a snapshot of a mirrored volume just as you would create a

snapshot of a linear or striped logical volume. For information on creating snapshot volumes, see

Section 4.4.4, “Creating Snapshot Volumes”.

• When extending an LVM volume, you can now use the --alloc cling option of the lvextend

command to specify the cling allocation policy. This policy will choose space on the same physical

volumes as the last segment of the existing logical volume. If there is insufficient space on the

physical volumes and a list of tags is defined in the lvm.conf file, LVM will check whether any

of the tags are attached to the physical volumes and seek to match those physical volume tags

between existing extents and new extents.

For information on extending LVM mirrored volumes with the --alloc cling option of the

lvextend command, see Section 4.4.12.2, “Extending a Logical Volume with the cling Allocation

Policy”.

• You can now specify multiple --addtag and --deltag arguments within a single pvchange,

vgchange, or lvchange command. For information on adding and removing object tags, see

Section C.1, “Adding and Removing Object Tags”.

• The list of allowed characters in LVM object tags has been extended, and tags can contain the

"/", "=", "!", ":", "#", and "&" characters. For information on LVM object tags, see Appendix C, LVM

Object Tags.

• You can now combine RAID0 (striping) and RAID1 (mirroring) in a single logical volume. Creating

a logical volume while simultaneously specifying the number of mirrors (--mirrors X) and

the number of stripes (--stripes Y) results in a mirror device whose constituent devices are

striped. For information on creating mirrored logical volumes, see Section 4.4.3, “Creating Mirrored

Volumes”.

• As of the Red Hat Enterprise Linux 6.1 release, if you need to create a consistent backup of data on

a clustered logical volume you can activate the volume exclusively and then create the snapshot.

For information on activating logical volumes exclusively on one node, see Section 4.7, “Activating

Logical Volumes on Individual Nodes in a Cluster”.

1.1.3. New and Changed Features for Red Hat Enterprise Linux 6.2

Red Hat Enterprise Linux 6.2 includes the following documentation and feature updates and changes.

• The Red Hat Enterprise Linux 6.2 release supports the issue_discards parameter in the

lvm.conf configuration file. When this parameter is set, LVM will issue discards to a logical

volume's underlying physical volumes when the logical volume is no longer using the space on the

physical volumes. For information on this parameter, refer to the inline documentation for the /etc/

lvm/lvm.conf file, which is also documented in Appendix B, The LVM Configuration Files.

1.2. Logical Volumes