Red Hat GFS 6.0 -, Administrator'S Manual

Page: 65 / 192

Chapter 6. Creating the Cluster Configuration System Files 51
fence_devices {
admin {
agent = "fence_manual"
}
}
Example 6-12. Manual Fencing Device Named
admin
Warning
Manual fencing should not be used in a production environment. Manual fencing depends on human
intervention whenever a node needs recovery. Cluster operation is halted during the intervention.
6.7. Creating the
nodes.ccs
File
The
nodes.ccs
file specifies the nodes that run in a GFS cluster and their fencing methods. The nodes
specified include those that run GFS and those that run LOCK_GULM servers. The
nodes.ccs
file
is used in conjunction with the
fence.ccs
file to configure fencing in a cluster; the
nodes.ccs
file
specifies fencing devices that are defined in the
fence.ccs
file.
Creating the
nodes.ccs
file consists of specifying the identity and fencing method (or methods) of
each node in a GFS cluster. Specifying the identity consists of assigning a name and an IP address
to the node. Specifying a fencing method consists of assigning a name to the fencing method and
specifying its fencing-device parameters; that is, specifying how a node is fenced.
The way in which a fencing method is specified depends on if a node has either dual power supplies or
multiple paths to FC storage. If a node has dual power supplies, then the fencing method for the node
must specify at least two fencing devices — one fencing device for each power supply. Similarly, if a
node has multiple paths to FC storage, then the fencing method for the node must specify one fencing
device for each path to FC storage. For example, if a node has two paths to FC storage, the fencing
method should specify two fencing devices — one for each path to FC storage. If a node has neither
dual power supplies nor multiple paths to FC storage, then the fencing method for the node should
specify only one fencing device.
You can configure a node with one fencing method or multiple fencing methods. When you configure
a node for one fencing method, that is the only fencing method available for fencing that node. When
you configure a node for multiple fencing methods, the fencing methods are cascaded from one fenc-
ing method to another according to the order of the fencing methods specified in the
nodes.ccs
file.
If a node fails, it is fenced using the first fencing method specified in the
nodes.ccs
file for that node.
If the first fencing method is not successful, the next fencing method specified for that node is used.
If none of the fencing methods is successful, then fencing starts again with the first fencing method
specified, and continues looping through the fencing methods in the order specified in
nodes.ccs
until the node has been fenced.
Refer to Chapter 10
Using the Fencing System for basic fencing details, descriptions of how fencing
is used, and descriptions of available fencing methods.