Managing Serviceguard 13th Edition, February 2007

Understanding Serviceguard Software Components
Responses to Failures
Chapter 3 131
For more information on cluster failover, see the white paper Optimizing
Failover Time in a Serviceguard Environment at
http://www.docs.hp.com->High
Availability->Serviceguard->White Papers.
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 failover packages currently running on that node to an
adoptive node elsewhere in the cluster. (System multi-node and
multi-node packages do not failover.)
The new location for each failover 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 swiftly 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, a local switch is done to a standby
LAN interface if one exists. If a heartbeat LAN interface fails and no
standby or redundant heartbeat is configured, the node fails with a TOC.
If a monitored data LAN interface fails without a standby, the node fails
with a TOC only if NODE_FAILFAST_ENABLED (described further in
“Package Configuration Planning” on page 165) is set to YES for the
package. Otherwise any packages using that LAN interface will be
halted and moved to another node if possible.
Disk protection is provided by separate products, such as Mirrordisk/UX
in LVM or VERITAS mirroring in VxVM and related products. In
addition, separately available EMS disk monitors allow you to notify
operations personnel when a specific failure, such as a lock disk failure,
takes place. Refer to the manual Using High Availability Monitors (HP
part number B5736-90046) for additional information; you can find it at
http://www.docs.hp.com->11i v2->HP-UX 11i v2 Enterprise
Operating Environment->Event Monitoring Service and HA
Monitors.