Using High Availability Monitors (June 2007)

Monitoring Disk Resources
Rules for Using the HA Disk Monitor with ServiceGuard
Chapter 2 43
# vgcreate -g bus1 /dev/vgdatabase /dev/dsk/c0t15d0
# vgextend -g bus2 /dev/vgdatabase /dev/dsk/c0t3d0
LVM will now recognize the I/O channel represented by /dev/dsk/
c0t15d0 as the primary link to the disk; if the primary link fails, LVM
will automatically switch to the alternate I/O channel represented by
/dev/dsk/c1t3d0.
Creating Logical Volumes
Use the following command to create logical volumes (the example is for
/dev/vgdatabase):
# lvcreate -L 120 -m 1 -s g /dev/vgdatabase
If you are using disk arrays in RAID 1 or RAID 5 mode, omit the -m 1
option.
This command creates a 120 MB mirrored volume named lvol1. The
name is supplied by default, since no name is specified in the command.
The -s g option means that mirroring is PVG-strict, that is, the mirror
copies of data will be in different physical volume groups.
Rules for Mirrored Individual Disks
The following rules apply to configuring mirrored disks for use with
ServiceGuard and the HA Disk Monitor:
• Mirroring must be PVG-strict.
Mirrored volumes must reside on a different bus from the original
volume to avoid a single point of failure and to obtain the best
pv_summary value for that mirror. This is done automatically by LVM
if you have created the PVGs while setting up mirroring. See the
lvextend manpage and Managing MC/ServiceGuard (HP Part
Number B3936-90026) for more information.
• Logical volumes that are 2-way mirrored should be in separate
volume groups from those that are 3-way mirrored.
Putting differently mirrored volumes in the same volume group
makes it difficult to accurately interpret the pv_summary data. Take
the example of a volume group containing both 2- and 3-way
mirroring. If 2 host adapters fail on that volume group, it could mean