Managing Systems and Workgroups: A Guide for HP-UX System Administrators

Administering a System: Managing Disks and Files
Managing File Systems
Chapter 6630
Doing an Online Backup by Splitting a Logical Volume
You can split a mirrored logical volume into two logical volumes to
perform a backup on an offline copy while the other copy stays online.
When you complete the activity on the offline copy, you can merge the
two logical volumes back into one. In order to bring the two copies back
in sync, LVM updates the physical extents in the offline copy based on
changes made to the copy that remained in use.
You can use SAM to split and merge logical volumes, or use lvsplit and
lvmerge.
After splitting a logical volume that contains a file system, you must
1. Perform a file system consistency check on the logical volume to be
backed up using the fsck command.
2. Mount the file system.
3. Back it up.
4. Unmount it.
5. Merge it back with the online copy.
See lvsplit (1M) and lvmerge (1M) for more details.
Achieving I/O Channel Separation
To achieve I/O channel separation, you can either use SAM to create
physical volume groups from a subset of LVM disks within a volume
group, or use the following commands after completing steps 1 through 3
under “Example: Creating a Logical Volume Using HP-UX Commands”
on page 575.
1. Create a physical volume group within a new volume group by
naming the physical volume group using the -g option of vgcreate
(1M).
2. Extend your volume group to contain another physical volume group
using the -g option of vgextend (1M).
To create a mirrored logical volume across physical volume groups
completing I/O channel separation, you set strict allocation to apply to
the disks that have been separated into physical volume groups. You set
the allocation policy when you create the logical volume, either with
SAM or with the lvcreate (1M) command.