HP Integrity Virtual Machines 4.2: Installation, Configuration, and Administration

11.2.4 Usage Considerations
VMs as Serviceguard Nodes configurations should be considered whenever there is a need for
consolidating systems in Serviceguard clusters, and the applications require full HA monitoring
and failover functionality that is provided by Serviceguard. These configurations allow for a
reduction in the total number of physical systems required for clusters by moving cluster nodes
from individual physical systems to multiple VMs running on single systems.
As with VMs as Serviceguard Packages configurations, Integrity VM Host nodes should run
only virtual machines and not other user applications. Doing so could adversely affect the
allocation of system resources to the VM guests running on the VM Hosts.
Monitoring of applications within a VMs as Node configuration is the same as in a traditional
Serviceguard cluster, because Serviceguard is running within the virtual machine. No specialized
monitoring agents are required as is the case for VMs as Package configurations.
Package failover times for VMs as Serviceguard Node configurations are similar to traditional
Serviceguard cluster failovers, because application packages are simply restarted on their
pre-configured adoptive nodes. These configurations do not experience the additional virtual
machine boot time that is part of VMs as Package configurations, where the failed over virtual
machine package must restart the virtual machine on its adoptive node.
Integrity VM has a default 5-second network polling interval that increases Serviceguard failover
time by several seconds. To insure the vswitches used by Serviceguard failover is less than 5
seconds, this polling interval can be set when using Serviceguard with Integrity VM to a
recommended value of 2-seconds by modifying the HPVMNETINTVAL=n parameter in the file
/etc/rc.config.d/hpvmconf.
NOTE: The value n is an integer between 1 and 10 that specifies the number of seconds for the
polling interval.
11.2.5 Cluster Reformation
Cluster-reformation time is somewhat longer for VMs as Serviceguard Node configurations
(approximately 40-70 seconds longer compared to a Serviceguard cluster consisting only of
physical nodes). This allows for all outstanding I/O requests from the VM through the VM Host
virtualization layer to complete before cluster activities can resume following a cluster reformation.
Serviceguard uses an io_timeout_extension parameter that is set at cluster-configuration time to
extend the quiescence period of the cluster reformation based on whether a VM node is present
in the cluster and the I/O timeout settings on the VM Host. It is important to note the following:
• The io_timeout_extension parameter is set internally by Serviceguard and is not configurable
by the user; however its value can be viewed using the Serviceguard cmviewconf, cmviewcl
v f commands, or can be found in the system log file.
• HP highly recommends that you install the VM management software, especially on VM
functioning as Serviceguard nodes, for Serviceguard to determine an optimal
io_timeout_extension value (otherwise, Serviceguard assumes the most conservative value
of 70 seconds resulting in unnecessarily lengthening the cluster recovery time).
• Be aware that the online addition or removal of VM cluster nodes or changes to cluster
membership parameters (available with the Serviceguard A.11.18 and later releases) can
affect the cluster quiescence period.
In a failure scenario where the pending I/Os from a VM are not cleared within its extended
quiescence time period, the Integrity VM software performs a TOC (Transfer of Control, or
CPU reset) on the VM Host servicing the guest to ensure data integrity by terminating any
outstanding I/O requests from the affected VM.
When performing a Serviceguard cluster consolidation, as with any workload consolidation
using Integrity VM, careful planning of the VM configuration is required to ensure proper
performance of the virtual machines by having a sufficient number of processors and available
190 Using HP Serviceguard with Integrity VM