Novell LINUX ENTERPRISE 11 - HIGH AVAILABILITY, Руководство пользователя, Страница: 76 / 298

meta target-role=Stopped \
operations my_stonith-operations \
op monitor start-delay=15 timeout=15 hostlist='' \
pduip='' community=''
5.5 Configuring Resource Constraints
Having all the resources configured is only one part of the job. Even if the cluster knows
all needed resources, it might still not be able to handle them correctly. For example,
it would not make sense to try to mount the file system on the slave node of drbd (in
fact, this would fail with drbd). To inform the cluster about these things, define con-
straints.
In High Availability, there are three different kinds of constraints available:
• Locational constraints that define on which nodes a resource may be run (in the
crm
shell with the command
location
).
• Collocational constraints that tell the cluster which resources may or may not run
together on a node (
colocation
).
• Ordering constraints to define the sequence of actions ( order
).
5.5.1 Locational Constraints
This type of constraint may be added multiple times for each resource. All
rsc_location
constraints are evaluated for a given resource. A simple example
that increases the probability to run a resource with the ID
fs1-loc
on the node with
the name
earth
to 100 would be the following:
crm(live)configure# location fs1-loc fs1 100: earth
5.5.2 Collocational Constraints
The
colocation
command is used to define what resources should run on the same
or on different hosts. Usually it is very common to use the following sequence:
66 High Availability Guide