HP-UX 11i v3 Using LVM Logical Volume Snapshots (September 2010)

29
Configurable location for the volume group configuration file
Because of the increased on-disk metadata size for a Version 2.2 volume group, the configuration file
size can also increase each time a snapshot is created. For more information on the size of
configuration file when snapshots are configured, see
Configuration file size
The default location where the configuration file is stored is /etc/lvmconf. The space in the /etc
file system might not be sufficient to store the configuration file of too many Version 2.2 volume
groups with large snapshot capacity and several snapshots configured. To overcome this problem,
you can configure the location of the configuration file with the LVMCONFPATH_NON_BOOT variable
defined in file /etc/lvmrc. To configure the default location for backing up a volume group
configuration for Version 2.2 and above, edit the /etc/lvmrc file and set the variable to the
appropriate location to be used to store the configuration files. After you make this change, all future
configuration backups and restores use this location for Version 2.2 and higher volume groups. This
configuration is applicable only for non-bootable volume groups with Version 2.2 or higher.
For more information, see vgcfgbackup(1M) and vgcfgrestore(1M).
Limitations when using snapshots
When snapshot logical volumes are configured in a volume group, the following limitations to the
normal usage of the logical volumes and the volume group are in the HP-UX 11i v3 March 2010
Update release:
• Activation of a Version 2.2 volume group in shared mode fails if the volume group has snapshot
logical volumes configured.
• You cannot create snapshot logical volumes when the volume group is activated in shared mode.
• You cannot create snapshots off swap and dump logical volumes. You also cannot configure a
logical volume as a swap or dump logical volume if it has snapshots associated.
• You can create only fully allocated snapshots off root and boot logical volumes. You cannot create
space-efficient snapshot of such logical volumes. Also, you cannot configure a logical volume as a
root or boot logical volume if it has space-efficient snapshots associated.
• You cannot configure a snapshot logical volume as a root, boot, swap, or dump logical volume.
• You cannot create a snapshot of a snapshot logical volume.
• You can stripe a snapshot only if the original logical volume is striped. You cannot create a striped
snapshot of a non-striped logical volume, nor can you create a non-striped snapshot of a striped
logical volume.
• The scheduling policy is inherited from the original logical volume; you cannot change it.
• You cannot split a mirrored snapshot logical volume using lvsplit.
• You cannot specify a snapshot logical volume or an original logical volume with snapshots
associated in lvmerge.
• If a physical volume of a Version 2.2 volume group has pre-allocated extents on it, you cannot use
the automatic rebalance feature of pvmove on the physical volume.
• Beginning with the HP-UX 11iv3 September 2010 Update release, you can change the size and
number of mirrors of a logical volume if it has snapshots associated. However, you cannot reduce
the size of such a logical volume if it has at least one space efficient snapshot logical volume
associated with it. In the HP-UX 11iv3 March 2010 Update release, you cannot change the size
and number of mirrors of a logical volume if it has snapshots associated.
• You cannot
change the number of mirrors of a snapshot logical volume after the snapshot is created.
• You cannot change the unshare unit of the volume group after it is configured during the volume
group creation.