HP-UX Logical Volume Manager and MirrorDisk/UX Release Notes HP-UX 11i v3 (September 2011)

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
Alternatively, you can disable multipathing for all legacy device files with this command:
# scsimgr save_attr -a leg_mpath_enable=false
Note that this has no effect on multipathing through persistent device special files. For more
information, see scsimgr(1M).
Moving volume groups from HP-UX 11i v3 to previous HP-UX releases
If a volume group used on HP-UX 11i v3 is accessed from a system running a previous release of
HP-UX 11i, you might encounter these compatibility issues:
• Version 2.x volume groups: As noted in “Version 2.x volume groups” (page 9), Version 2.x
volume groups are not recognized on previous releases of HP-UX.
• Logical volumes larger than 2 TB: Releases prior to HP-UX 11i v3 can only access data within
the first 2 TB of a logical volume. If a logical volume larger than 2 TB is created on HP-UX 11i
v3, its use is not recommended on any previous HP-UX release. The volume group can be
activated and the logical volume can be used, but any data in that logical volume beyond 2
TB will be inaccessible.
NOTE: Patches PHKL_36745, PHCO_36744, and PHCO_37939 resolve this compatibility
issue for HP-UX 11i v2. Installing these patches enables the creation and use of logical volumes
up to 16 TB.
• Striped Mirrors: Releases prior to HP-UX 11i v3 only support extent-based striping via the -D
option to lvcreate. If a logical volume using simultaneous mirroring and non-extent-based
striping is created on HP-UX 11i v3, attempts to import or activate its associated volume group
will fail on a previous HP-UX release. To import the volume group, you must remove the
incompatible logical volumes or reduce them to a single mirror.
NOTE: Patches PHKL_36745, PHCO_36744, and PHCO_37939 resolve this compatibility
issue for HP-UX 11i v2. Installing these patches enables the creation and use of striped mirrors.
• Mirror Write Cache (MWC): When a volume group containing a logical volume using the
Mirror Write Cache is activated on HP-UX 11i v3, its Mirror Write Cache format is converted
to a new format. Importing or activating the volume group on a previous HP-UX release does
not recognize the new format and triggers a full resynchronization of the mirrors.
10 Logical Volume Manager and MirrorDisk/UX Release Notes