LVM Migration from Legacy to Agile Naming Model

Legacy and Agile Naming Models
In versions prior to HP-UX 11i v3, the Device Special Files (DSFs) of mass storage devices were bound to the path
of the device. This representation of mass storage devices still exists in HP-UX 11i v3, and is referred as the
legacy view. HP-UX 11i v3 introduces a new representation for mass storage devices called the agile view.
In this representation, the DSFs of mass storage devices are bound to the device World Wide Identifier (WWID)
making them persistent (that is, each LUN is uniquely identified by a single DSF, irrespective of the number of
lunpaths and independent of any physical path changes). The agile view coexists with the legacy view and both
types of DSFs can be used to access a given mass storage device independently and simultaneously. For
additional information on the next generation mass storage subsystem in HP-UX 11i v3, see the
For More
Information section for the white paper The Next Generation Mass Storage Stack.
Typical legacy and persistent DSFs for a LUN are shown below:
Legacy DSF: /dev/dsk/c8t1d3 and /dev/rdsk/c8t1d3
Persistent DSF: /dev/disk/disk66 and /dev/rdisk/disk66
LVM support for Dual Naming Models
In the HP-UX 11i v3 release, LVM supports both legacy and persistent DSFs. A volume group can be configured
using both styles of DSFs. On a system, some volume groups can use legacy DSFs, some can use persistent DSFs
and the rest a mix of legacy and persistent DSFs. Supporting a mixed mode configuration allows a volume group
that currently uses one DSF naming model to be extended (by vgextend) with the same or another physical volume
using a different DSF naming model. Such operations result in a mixed mode volume group and facilitate a
phased DSF migration from legacy to agile naming model.
LVM commands pvcreate, vgcreate and vgextend are backward compatible, and work transparently with both
legacy and persistent DSFs. New options have been added to vgimport and vgscan to select the persistent DSF
naming model.
HP highly recommends using persistent DSFs for LVM configurations.
All new volume groups should be configured with persistent DSFs only. Existing volume groups configured with
legacy DSFs should be migrated (re-configured) to use corresponding persistent DSFs. The migration of volume
groups from legacy DSF naming model to persistent DSF naming model can be achieved in several ways. A script
named vgdsf is also made available to assist in the DSF migration process.
Naming Model specific Commands/Options
New options have been added to vgimport (option -N) and vgscan (options –N and –B), to specify the persistent
naming model. Given below is a summary of these options, and for details, refer to the respective command man
pages.
vgimport –N
Configure the volume group using persistent DSFs. In the absence of the -N option, legacy
DSFs are used. This option can only be used together with the scan option, –s.
vgscan –N
Recover /etc/lvmtab file using persistent DSFs, with the following exception: Active volume
groups configured with legacy DSFs. In this case, vgscan populates the /etc/lvmtab file
using legacy DSFs.
vgscan –B
Recover /etc/lvmtab file using both persistent and legacy DSFs. This option can be used
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