HP-UX Logical Volume Manager and MirrorDisk/UX Release Notes (762804-001, March 2014)

1.6 Compatibility issues
1.6.1 Version 2.x volume groups
• Version 2.2 volume groups are not recognized on previous releases of HP-UX, including
versions of HP-UX 11i v3 prior to the March 2010 Update release. Version 2.1 volume groups
are not recognized on previous releases of HP-UX, including versions of HP-UX 11i v3 prior
to the September 2008 release. Version 1.0 volume groups are supported on all supported
versions of HP-UX, including 11i v1, 11i v2, and 11i v3.
• The following HP-UX product does not currently support Version 2.x volume groups:
◦ HP Process Resource Manager (HP PRM)
This product plans to add support of Version 2.x volume groups. For the most recent information
on this products, see the IT Resource Center (ITRC) at www.hp.com/go/hpsc, or consult the
release notes for the specific product.
• Encrypted Volume and File System (EVFS) v1.1 and greater supports Version 2.x volume
groups.
1.6.2 Using LVM boot disks of size greater than 2TB (terabytes)
There are specific software (patches) and hardware (HBAs) prerequisites for using LVM boot disks
of size greater than 2TB. Also, there are compatibility issues when administrating such boot disks
in releases prior to HP-UX 11i v3 March 2013. For more information about managing boot disks
of size greater than 2 TB, see the LVM System Administration Guide at http://www.hp.com/go/
hpux-LVM-VxVM-docs.
1.6.3 Moving from HP-UX 11i v2 to HP-UX 11i v3
If you are migrating a system from HP-UX 11i v2 to HP-UX 11i v3, see the LVM migration white
paper described in “Related documentation”. It contains information on migrating an LVM
configuration from the legacy naming model to the agile naming model.
Existing LVM configurations created on HP-UX 11i v2 continue to work on HP-UX 11i v3 under the
legacy naming model. However, there is a change in behavior for Alternate Links (PVLinks):
In HP-UX 11i v3, management of multipathed devices is available outside of LVM using the next
generation mass storage stack. By default, the next generation mass storage stack distributes I/O
requests across all available paths to a multipathed disk, even when using legacy device special
files. Using LVM with persistent or legacy device special files might cause I/O requests to be sent
across alternate links, even if the links are not configured as PVLinks; this does not introduce any
errors, but it does differ from PVLink behavior in previous releases.
When using LVM configuration commands on legacy device special files, LVM does not select an
alternate path if the path corresponding to the specified device special file is unavailable, unless
the unavailable path and the alternate path are configured as part of an active volume group.
When using LVM configuration commands on persistent device special files, LVM succeeds if at
least one of the paths to the device is available.
HP recommends converting volume groups with multipathed disks to persistent device special files
and using native multipathing, as described in the migration white paper in “Related
documentation”.
However, if you want backward-compatible PVLink behavior, you must use legacy device special
files for physical volumes, and disable the mass storage stack multipathing for those physical
volumes. To disable multipathing on legacy device special files, use the scsimgr command to
configure a global device tunable called leg_mpath_enable.
For each multipathed disk, enter the following command:
# scsimgr save_attr -D /dev/rdisk/diskn -a leg_mpath_enable=false
12 Logical Volume Manager and MirrorDisk/UX release notes