You can define how a mirrored logical volume behaves in the event of a device failure with the mirror_image_fault_policy and mirror_log_fault_policy parameters in the activation section of the lvm.conf file. When this parameter is set to remove, the system attempts to remove the faulty device and run without it. When this parameter is set to allocate, the system attempts to remove the faulty device and tries to allocate space on a new device to be a replacement for the failed device; this policy acts like the remove policy if no suitable device and space can be allocated for the replacement. For information on the LVM mirror failure policies, see Section 4.4.3.1, “Mirrored Logical Volume Failure Policy”.

For the Red Hat Enterprise Linux 6 release, the Linux I/O stack has been enhanced to process vendor-provided I/O limit information. This allows storage management tools, including LVM, to optimize data placement and access. This support can be disabled by changing the default values of data_alignment_detection and data_alignment_offset_detection in the lvm.conf file, although disabling this support is not recommended.

For information on data alignment in LVM as well as information on changing the default values of data_alignment_detection and data_alignment_offset_detection, see the inline documentation for the /etc/lvm/lvm.conf file, which is also documented in Appendix B, The LVM Configuration Files. For general information on support for the I/O Stack and I/O limits in Red Hat Enterprise Linux 6, see the Storage Administration Guide.

In Red Hat Enterprise Linux 6, the Device Mapper provides direct support for udev integration. This synchronizes the Device Mapper with all udev processing related to Device Mapper devices, including LVM devices. For information on Device Mapper support for the udev device manager, see Section A.3, “Device Mapper Support for the udev Device Manager”.

For the Red Hat Enterprise Linux 6 release, you can use the lvconvert --repair command to repair a mirror after disk failure. This brings the mirror back into a consistent state. For information on the lvconvert --repair command, see Section 4.4.3.3, “Repairing a Mirrored Logical Device”.

As of the Red Hat Enterprise Linux 6 release, you can use the --merge option of the lvconvert command to merge a snapshot into its origin volume. For information on merging snapshots, see Section 4.4.5, “Merging Snapshot Volumes”.

As of the Red Hat Enterprise Linux 6 release, you can use the --splitmirrors argument of the lvconvert command to split off a redundant image of a mirrored logical volume to form a new logical volume. For information on using this option, see Section 4.4.3.2, “Splitting Off a Redundant Image of a Mirrored Logical Volume”.

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”.

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”.

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.