LVM Version 2.0 Volume Groups in HP-UX 11i v3 (September 2008)
Size of logical volume or number of mirrors
To reach the new limits, increase the values passed in to lvcreate, lvextend, or FSWEB.
Migration Between1.0, 2.0, and 2.1
Why would a user migrate?
You might want to migrate from 1.0 to 2.1 because your1.0 volume group is too small. You can use vgmodify to
extend the limits of a 1.0 volume group, but that might not work or might not be enough. HP does not recommend
migration from 1.0 to 2.0, instead migrate to 2.1.
Migrating to a lower volume group version (2.x to 1.0 or 2.1 to 2.0) is impossible as soon as the limits of the
destination version are exceeded. For example a 2.0 volume group containing 256 logical volumes (one more
than the 1.0 limit) cannot be migrated to 1.0.
How to migrate?
At this time, there is no in-place migration available. You must migrate by copying data (for example, with dd) to
another volume group created with the desired version.
You face the same situation when you cannot increase the size of a 1.0 volume group and vgmodify cannot do it
either. You must copy over the data to a new volume group.
To speed up the copy, you can issue several dd commands in parallel on different volume groups or different parts
of volume groups.
When to migrate?
Because the migration is done by copy, a good time to migrate is when you replace your storage.
High Availability
With version 2.x volume groups, you now have the ability to provide additional copies of user data, increasing
the availability of your data. 1.0 volume groups are limited to two mirrors (three replicas of the data). 2.x volume
groups can have up to five mirrors (six replicas of the data).
When Does it Make Sense to Use More Than Two Mirrors?
Using more than three replicas of the data makes sense as part of a setup for disaster recovery.
The following two examples show a logical volume whose data is replicated six times. Figure 7 shows a two site
setup. In this case, if one site goes down the data stays highly available on the surviving site because it is
replicated three times on that site.
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