Managing HP Serviceguard for Linux, Tenth Edition, September 2012

group vg02 and the Package2 IP address) as quickly as possible, SystemB halts
(system reset).
NOTE: If AUTOSTART_CMCLD in /etc/rc.config.d/cmcluster ($SGAUTOSTART)
is set to zero, the node will not attempt to join the cluster when it comes back up.
For more information on cluster failover, see the white paper Optimizing Failover Time
in a Serviceguard Environment (version A.11.19 and later) at http://
www.docs.hp.com -> High Availability -> Serviceguard -> White
Papers. For troubleshooting information, see “Cluster Re-formations Caused by
MEMBER_TIMEOUT Being Set too Low” (page 300).
Responses to Hardware Failures
If a serious system problem occurs, such as a system panic or physical disruption of the
SPU's circuits, Serviceguard recognizes a node failure and transfers the packages currently
running on that node to an adoptive node elsewhere in the cluster. (System multi-node
and multi-node packages do not fail over.)
The new location for each package is determined by that package's configuration file,
which lists primary and alternate nodes for the package. Transfer of a package to another
node does not transfer the program counter. Processes in a transferred package will
restart from the beginning. In order for an application to be expeditiously restarted after
a failure, it must be “crash-tolerant”; that is, all processes in the package must be written
so that they can detect such a restart. This is the same application design required for
restart after a normal system crash.
In the event of a LAN interface failure, bonding provides a backup path for IP messages.
If a heartbeat LAN interface fails and no redundant heartbeat is configured, the node
fails with a reboot. If a monitored data LAN interface fails, the node fails with a reboot
only if node_fail_fast_enabled (described further under “Configuring a Package:
Next Steps” (page 154)) is set to yes for the package. Otherwise any packages using
that LAN interface will be halted and moved to another node if possible (unless the LAN
recovers immediately; see “When a Service or Subnet Fails, or a Dependency is Not
Met” (page 64)).
Disk monitoring provides additional protection. You can configure packages to be
dependent on the health of disks, so that when a disk monitor reports a problem, the
package can fail over to another node. See “Creating a Disk Monitor Configuration”
(page 231).
Serviceguard does not respond directly to power failures, although a loss of power to
an individual cluster component may appear to Serviceguard like the failure of that
component, and will result in the appropriate switching behavior. Power protection is
provided by HP-supported uninterruptible power supplies (UPS).
88 Understanding Serviceguard Software Components