Novell LINUX ENTERPRISE 11 - HIGH AVAILABILITY, Manual, Page: 93 / 298

Blade Power Control Devices
If you are running a cluster on a set of blades, then the power control device in the
blade enclosure is the only candidate for fencing. Of course, this device must be
capable of managing single blade computers.
Lights-out Devices
Lights-out devices (IBM RSA, HP iLO, Dell DRAC) are becoming increasingly
popular, and in the future they may even become standard on off-the-shelf comput-
ers. However, they are inferior to UPS devices, because they share a power supply
with their host (a cluster node). If a node stays without power, the device supposed
to control it would be just as useless. In that case, the CRM would continue its at-
tempts to fence the node indefinitely, as all other resource operations would wait
for the fencing/STONITH operation to complete.
Testing Devices
Testing devices are used exclusively for testing purposes. They are usually more
gentle on the hardware. Once the cluster goes into production, they must be replaced
with real fencing devices.
The choice of the STONITH device depends mainly on your budget and the kind of
hardware you use.
8.2.2 STONITH Implementation
The STONITH implementation of SUSE® Linux Enterprise High Availability Extension
consists of two components:
stonithd
stonithd is a daemon which can be accessed by local processes or over the network.
It accepts the commands which correspond to fencing operations: reset, power-off,
and power-on. It can also check the status of the fencing device.
The stonithd daemon runs on every node in the CRM HA cluster. The stonithd in-
stance running on the DC node receives a fencing request from the CRM. It is up
to this and other stonithd programs to carry out the desired fencing operation.
STONITH Plug-ins
For every supported fencing device there is a STONITH plug-in which is capable
of controlling said device. A STONITH plug-in is the interface to the fencing device.
Fencing and STONITH 83