Managing HP Serviceguard for Linux, Tenth Edition, September 2012

Volume Groups and Physical Volume Worksheet
You can organize and record your physical disk configuration by identifying which
physical disks, LUNs, or disk array groups will be used in building each volume group
for use with high availability applications. Use the Volume Group and Physical Volume
worksheet (page 325).
NOTE: HP recommends that you use volume group names other than the default volume
group names (vg01, vg02, etc.). Choosing volume group names that represent the high
availability applications they are associated with (e.g., /dev/vgdatabase) will simplify
cluster administration.
Cluster Configuration Planning
A cluster should be designed to provide the quickest possible recovery from failures. The
actual time required to recover from a failure depends on several factors:
• The length of the MEMBER_TIMEOUT; see the description of this parameter under
“Cluster Configuration Parameters ” for recommendations.
• The design of the run and halt instructions in the package control script. They should
be written for fast execution.
• The application and database recovery time. They should be designed for the shortest
recovery time.
In addition, you must provide consistency across the cluster so that:
• User names are the same on all nodes.
• UIDs are the same on all nodes.
• GIDs are the same on all nodes.
• Applications in the system area are the same on all nodes.
• System time is consistent across the cluster.
• Files that could be used by more than one node, such as /usr or/opt files, must
be the same on all nodes.
Heartbeat Subnet and Cluster Re-formation Time
The speed of cluster re-formation depends on the number of heartbeat subnets.
If the cluster has only a single heartbeat network, and a network card on that network
fails, heartbeats will be lost while the failure is being detected and the IP address is being
switched to a standby interface. The cluster may treat these lost heartbeats as a failure
and re-form without one or more nodes. To prevent this, a minimum MEMBER_TIMEOUT
value of 14 seconds is required for clusters with a single heartbeat network.
Cluster Configuration Planning 99