LVM Migration from Legacy to Agile Naming Model

Volume Group DSF Migration

In HP-UX 11i v3, HP recommends the use of persistent DSFs over legacy, in LVM volume group configurations. A

migration operation is required for existing volume groups already configured with legacy DSFs. Migration

involves reconfiguration of existing volume groups with corresponding persistent DSFs, in place of legacy DSFs.

DSF migration should be performed one volume group at a time, and should be completed for all volume groups.

All volume groups configured with legacy DSFs can be migrated, irrespective of the volume group state

(activated/de-activated, shared/standalone, with/without alternate links). Volume groups can be migrated using

any of the following methods:

Note: The migration changes only the DSFs. Volume group information and layout is not altered in any way.

Note: /etc/lvmpvg is an optional ASCII file (refer to lvmpvg(4) manual page) that stores the physical volume

group (PVG) information. /etc/lvmtab is a binary file that stores the association between physical volumes and

the corresponding volume group. Both these files support legacy and persistent DSFs and must be updated as part

of the migration operation.

Migration Alternatives

All of the migration alternatives listed below automatically update the /etc/lvmtab file to reflect the newer

configuration and no explicit user action is required. However, some alternatives require that the PVG information

in /etc/lvmpvg file be updated manually. Please refer to the information on /etc/lvmpvg file, listed in each of the

alternatives.

Any one of the below alternatives can be used to migrate a volume group. HP recommends using the vgdsf script

(

alternative 3) for migration.

Note: Each alternative updates one volume group at a time. The steps must be repeated in the alternative chosen

for all volume groups to be migrated.

1. Backup the /etc/lvmpvg file, if it exists. Deactivate and export the volume group. Re-import the same volume

group using persistent DSFs in place of legacy DSFs. Persistent DSFs, corresponding to legacy DSFs, can be

found using ioscan –m dsf <legacy_dsf> command. Restore the backed-up /etc/lvmpvg file and replace

legacy DSFs listed under the volume group being migrated with corresponding persistent DSFs (In case of

multi-path devices, a single persistent DSF can correspond to multiple legacy DSFs). The disadvantage of this

method is the necessity of volume group deactivation.

2. Run vgscan –B command followed by volume group activation.

For each of the physical volumes configured in the volume group, vgscan -B command populates the

/etc/lvmtab file with both persistent and legacy DSFs. However, /etc/lvmtab file supports a maximum of 8

paths per physical volume. Therefore, if a physical volume has more than 8 paths configured, only 7 are

retained in order to allow space for the addition of persistent DSF.

Note: The vgscan command will not update existing volume group entries in /etc/lvmtab file unless the -f

option is used. The -f option restricts the operation to the specified volume group (overwrite existing volume

group entries in /etc/lvmtab). If the /etc/lvmtab file is moved to a new location before running the vgscan -B

command, full effect of the command is taken on all configured volume groups and /etc/lvmtab file gets re-

created.