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diff --git a/doc/Pacemaker_Explained/en-US/Ch-Advanced-Resources.txt b/doc/Pacemaker_Explained/en-US/Ch-Advanced-Resources.txt
index 6a280387e4..77b854696d 100644
--- a/doc/Pacemaker_Explained/en-US/Ch-Advanced-Resources.txt
+++ b/doc/Pacemaker_Explained/en-US/Ch-Advanced-Resources.txt
@@ -1,937 +1,937 @@
= Advanced Resource Types =
[[group-resources]]
== Groups - A Syntactic Shortcut ==
indexterm:[Group Resources]
indexterm:[Resources,Groups]
One of the most common elements of a cluster is a set of resources
that need to be located together, start sequentially, and stop in the
reverse order. To simplify this configuration we support the concept
of groups.
.An example group
======
[source,XML]
-------
<group id="shortcut">
<primitive id="Public-IP" class="ocf" type="IPaddr" provider="heartbeat">
<instance_attributes id="params-public-ip">
<nvpair id="public-ip-addr" name="ip" value="1.2.3.4"/>
</instance_attributes>
</primitive>
<primitive id="Email" class="lsb" type="exim"/>
</group>
-------
======
Although the example above contains only two resources, there is no
limit to the number of resources a group can contain. The example is
also sufficient to explain the fundamental properties of a group:
* Resources are started in the order they appear in (+Public-IP+
first, then +Email+)
* Resources are stopped in the reverse order to which they appear in
(+Email+ first, then +Public-IP+)
If a resource in the group can't run anywhere, then nothing after that
is allowed to run, too.
* If +Public-IP+ can't run anywhere, neither can +Email+;
* but if +Email+ can't run anywhere, this does not affect +Public-IP+
in any way
The group above is logically equivalent to writing:
.How the cluster sees a group resource
======
[source,XML]
-------
<configuration>
<resources>
<primitive id="Public-IP" class="ocf" type="IPaddr" provider="heartbeat">
<instance_attributes id="params-public-ip">
<nvpair id="public-ip-addr" name="ip" value="1.2.3.4"/>
</instance_attributes>
</primitive>
<primitive id="Email" class="lsb" type="exim"/>
</resources>
<constraints>
<rsc_colocation id="xxx" rsc="Email" with-rsc="Public-IP" score="INFINITY"/>
<rsc_order id="yyy" first="Public-IP" then="Email"/>
</constraints>
</configuration>
-------
======
Obviously as the group grows bigger, the reduced configuration effort
can become significant.
Another (typical) example of a group is a DRBD volume, the filesystem
mount, an IP address, and an application that uses them.
=== Group Properties ===
.Properties of a Group Resource
[width="95%",cols="3m,5<",options="header",align="center"]
|=========================================================
|Field
|Description
|id
|Your name for the group
indexterm:[id,Group Resource Property]
indexterm:[Resource,Group Property,id]
|=========================================================
=== Group Options ===
Options inherited from <<s-resource-options,primitive>> resources:
+priority, target-role, is-managed+
=== Group Instance Attributes ===
Groups have no instance attributes, however any that are set here will
be inherited by the group's children.
=== Group Contents ===
Groups may only contain a collection of
<<primitive-resource>> cluster resources. To refer to
the child of a group resource, just use the child's id instead of the
group's.
=== Group Constraints ===
Although it is possible to reference the group's children in
constraints, it is usually preferable to use the group's name instead.
.Example constraints involving groups
======
[source,XML]
-------
<constraints>
<rsc_location id="group-prefers-node1" rsc="shortcut" node="node1" score="500"/>
<rsc_colocation id="webserver-with-group" rsc="Webserver" with-rsc="shortcut"/>
<rsc_order id="start-group-then-webserver" first="Webserver" then="shortcut"/>
</constraints>
-------
======
=== Group Stickiness ===
indexterm:[resource-stickiness,Groups]
Stickiness, the measure of how much a resource wants to stay where it
is, is additive in groups. Every active resource of the group will
contribute its stickiness value to the group's total. So if the
default +resource-stickiness+ is 100, and a group has seven members,
five of which are active, then the group as a whole will prefer its
current location with a score of 500.
[[s-resource-clone]]
== Clones - Resources That Get Active on Multiple Hosts ==
indexterm:[Clone Resources]
indexterm:[Resources,Clones]
Clones were initially conceived as a convenient way to start N
instances of an IP resource and have them distributed throughout the
cluster for load balancing. They have turned out to quite useful for
a number of purposes including integrating with Red Hat's DLM, the
fencing subsystem, and OCFS2.
You can clone any resource, provided the resource agent supports it.
Three types of cloned resources exist:
* Anonymous
* Globally Unique
* Stateful
Anonymous clones are the simplest type. These resources behave
completely identically everywhere they are running. Because of this,
there can only be one copy of an anonymous clone active per machine.
Globally unique clones are distinct entities. A copy of the clone
running on one machine is not equivalent to another instance on
another node. Nor would any two copies on the same node be
equivalent.
Stateful clones are covered later in <<s-resource-multistate>>.
.An example clone
======
[source,XML]
-------
<clone id="apache-clone">
<meta_attributes id="apache-clone-meta">
<nvpair id="apache-unique" name="globally-unique" value="false"/>
</meta_attributes>
<primitive id="apache" class="lsb" type="apache"/>
</clone>
-------
======
=== Clone Properties ===
.Properties of a Clone Resource
[width="95%",cols="3m,5<",options="header",align="center"]
|=========================================================
|Field
|Description
|id
|Your name for the clone
indexterm:[id,Clone Property]
indexterm:[Clone,Property,id]
|=========================================================
=== Clone Options ===
Options inherited from <<s-resource-options,primitive>> resources:
+priority, target-role, is-managed+
.Clone specific configuration options
[width="95%",cols="3m,5<",options="header",align="center"]
|=========================================================
|Field
|Description
|clone-max
|How many copies of the resource to start. Defaults to the number of
nodes in the cluster.
indexterm:[clone-max,Clone Option]
indexterm:[Clone,Option,clone-max]
|clone-node-max
|How many copies of the resource can be started on a single node;
default _1_.
indexterm:[clone-node-max,Clone Option]
indexterm:[Clone,Option,clone-node-max]
|notify
|When stopping or starting a copy of the clone, tell all the other
copies beforehand and when the action was successful. Allowed values:
_false_, +true+
indexterm:[notify,Clone Option]
indexterm:[Clone,Option,notify]
|globally-unique
|Does each copy of the clone perform a different function? Allowed
values: _false_, +true+
indexterm:[globally-unique,Clone Option]
indexterm:[Clone,Option,globally-unique]
|ordered
|Should the copies be started in series (instead of in
parallel). Allowed values: _false_, +true+
indexterm:[ordered,Clone Option]
indexterm:[Clone,Option,ordered]
|interleave
|Changes the behavior of ordering constraints (between clones/masters)
so that instances can start/stop as soon as their peer instance has
(rather than waiting for every instance of the other clone
has). Allowed values: _false_, +true+
indexterm:[interleave,Clone Option]
indexterm:[Clone,Option,interleave]
|=========================================================
=== Clone Instance Attributes ===
Clones have no instance attributes; however, any that are set here
will be inherited by the clone's children.
=== Clone Contents ===
Clones must contain exactly one group or one regular resource.
[WARNING]
You should never reference the name of a clone's child.
If you think you need to do this, you probably need to re-evaluate your design.
=== Clone Constraints ===
In most cases, a clone will have a single copy on each active cluster
node. If this is not the case, you can indicate which nodes the
cluster should preferentially assign copies to with resource location
constraints. These constraints are written no differently to those
for regular resources except that the clone's id is used.
Ordering constraints behave slightly differently for clones. In the
example below, +apache-stats+ will wait until all copies of the clone
that need to be started have done so before being started itself.
Only if _no_ copies can be started +apache-stats+ will be prevented
from being active. Additionally, the clone will wait for
+apache-stats+ to be stopped before stopping the clone.
Colocation of a regular (or group) resource with a clone means that
the resource can run on any machine with an active copy of the clone.
The cluster will choose a copy based on where the clone is running and
the resource's own location preferences.
Colocation between clones is also possible. In such cases, the set of
allowed locations for the clone is limited to nodes on which the clone
is (or will be) active. Allocation is then performed as normally.
.Example constraints involving clones
======
[source,XML]
-------
<constraints>
<rsc_location id="clone-prefers-node1" rsc="apache-clone" node="node1" score="500"/>
<rsc_colocation id="stats-with-clone" rsc="apache-stats" with="apache-clone"/>
<rsc_order id="start-clone-then-stats" first="apache-clone" then="apache-stats"/>
</constraints>
-------
======
=== Clone Stickiness ===
indexterm:[resource-stickiness,Clones]
To achieve a stable allocation pattern, clones are slightly sticky by
default. If no value for +resource-stickiness+ is provided, the clone
will use a value of 1. Being a small value, it causes minimal
disturbance to the score calculations of other resources but is enough
to prevent Pacemaker from needlessly moving copies around the cluster.
=== Clone Resource Agent Requirements ===
Any resource can be used as an anonymous clone, as it requires no
additional support from the resource agent. Whether it makes sense to
do so depends on your resource and its resource agent.
Globally unique clones do require some additional support in the
resource agent. In particular, it must only respond with
+${OCF_SUCCESS}+ if the node has that exact instance active. All
other probes for instances of the clone should result in
+${OCF_NOT_RUNNING}+. Unless of course they are failed, in which case
they should return one of the other OCF error codes.
Copies of a clone are identified by appending a colon and a numerical
offset, eg. +apache:2+.
Resource agents can find out how many copies there are by examining
the +OCF_RESKEY_CRM_meta_clone_max+ environment variable and which
copy it is by examining +OCF_RESKEY_CRM_meta_clone+.
You should not make any assumptions (based on
+OCF_RESKEY_CRM_meta_clone+) about which copies are active. In
particular, the list of active copies will not always be an unbroken
sequence, nor always start at 0.
==== Clone Notifications ====
Supporting notifications requires the +notify+ action to be
implemented. Once supported, the notify action will be passed a
number of extra variables which, when combined with additional
context, can be used to calculate the current state of the cluster and
what is about to happen to it.
.Environment variables supplied with Clone notify actions
[width="95%",cols="5,3<",options="header",align="center"]
|=========================================================
|Variable
|Description
|OCF_RESKEY_CRM_meta_notify_type
|Allowed values: +pre+, +post+
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,type]
indexterm:[type,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_operation
|Allowed values: +start+, +stop+
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,operation]
indexterm:[operation,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_start_resource
|Resources to be started
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,start_resource]
indexterm:[start_resource,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_stop_resource
|Resources to be stopped
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,stop_resource]
indexterm:[stop_resource,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_active_resource
|Resources that are running
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,active_resource]
indexterm:[active_resource,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_inactive_resource
|Resources that are not running
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,inactive_resource]
indexterm:[inactive_resource,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_start_uname
|Nodes on which resources will be started
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,start_uname]
indexterm:[start_uname,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_stop_uname
|Nodes on which resources will be stopped
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,stop_uname]
indexterm:[stop_uname,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_active_uname
|Nodes on which resources are running
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,active_uname]
indexterm:[active_uname,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_inactive_uname
|Nodes on which resources are not running
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,inactive_uname]
indexterm:[inactive_uname,Notification Environment Variable]
|=========================================================
The variables come in pairs, such as
+OCF_RESKEY_CRM_meta_notify_start_resource+ and
+OCF_RESKEY_CRM_meta_notify_start_uname+ and should be treated as an
array of whitespace separated elements.
Thus in order to indicate that +clone:0+ will be started on +sles-1+,
+clone:2+ will be started on +sles-3+, and +clone:3+ will be started
on +sles-2+, the cluster would set
.Example notification variables
======
[source,Bash]
-------
OCF_RESKEY_CRM_meta_notify_start_resource="clone:0 clone:2 clone:3"
OCF_RESKEY_CRM_meta_notify_start_uname="sles-1 sles-3 sles-2"
-------
======
==== Proper Interpretation of Notification Environment Variables ====
.Pre-notification (stop):
* Active resources: +$OCF_RESKEY_CRM_meta_notify_active_resource+
* Inactive resources: +$OCF_RESKEY_CRM_meta_notify_inactive_resource+
* Resources to be started: +$OCF_RESKEY_CRM_meta_notify_start_resource+
* Resources to be stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+
.Post-notification (stop) / Pre-notification (start):
* Active resources
** +$OCF_RESKEY_CRM_meta_notify_active_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+
* Inactive resources
** +$OCF_RESKEY_CRM_meta_notify_inactive_resource+
** plus +$OCF_RESKEY_CRM_meta_notify_stop_resource+
* Resources that were started: +$OCF_RESKEY_CRM_meta_notify_start_resource+
* Resources that were stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+
.Post-notification (start):
* Active resources:
** +$OCF_RESKEY_CRM_meta_notify_active_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+
** plus +$OCF_RESKEY_CRM_meta_notify_start_resource+
* Inactive resources:
** +$OCF_RESKEY_CRM_meta_notify_inactive_resource+
** plus +$OCF_RESKEY_CRM_meta_notify_stop_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_start_resource+
* Resources that were started: +$OCF_RESKEY_CRM_meta_notify_start_resource+
* Resources that were stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+
[[s-resource-multistate]]
== Multi-state - Resources That Have Multiple Modes ==
indexterm:[Multi-state Resources]
indexterm:[Resources,Multi-state]
Multi-state resources are a specialization of Clone resources; please
ensure you understand the section on clones before continuing! They
allow the instances to be in one of two operating modes; these are
called +Master+ and +Slave+, but can mean whatever you wish them to
mean. The only limitation is that when an instance is started, it
must come up in the +Slave+ state.
=== Multi-state Properties ===
.Properties of a Multi-State Resource
[width="95%",cols="3m,5<",options="header",align="center"]
|=========================================================
|Field
|Description
|id
|Your name for the multi-state resource
indexterm:[id,Multi-State Property]
indexterm:[Multi-State,Property,id]
|=========================================================
=== Multi-state Options ===
Options inherited from <<s-resource-options,primitive>> resources:
+priority+, +target-role+, +is-managed+
Options inherited from <<s-resource-clone,clone>> resources:
+clone-max+, +clone-node-max+, +notify+, +globally-unique+, +ordered+,
+interleave+
.Multi-state specific resource configuration options
[width="95%",cols="3m,5<",options="header",align="center"]
|=========================================================
|Field
|Description
|master-max
|How many copies of the resource can be promoted to +master+ status;
default 1.
indexterm:[master-max,Multi-State Option]
indexterm:[Multi-State,Option,master-max]
|master-node-max
|How many copies of the resource can be promoted to +master+ status on
a single node; default 1.
indexterm:[master-node-max,Multi-State Option]
indexterm:[Multi-State,Option,master-node-max]
|=========================================================
=== Multi-state Instance Attributes ===
Multi-state resources have no instance attributes; however, any that
are set here will be inherited by master's children.
=== Multi-state Contents ===
Masters must contain exactly one group or one regular resource.
[WARNING]
You should never reference the name of a master's child.
If you think you need to do this, you probably need to re-evaluate your design.
=== Monitoring Multi-State Resources ===
The normal type of monitor actions are not sufficient to monitor a
multi-state resource in the +Master+ state. To detect failures of the
+Master+ instance, you need to define an additional monitor action
with +role="Master"+.
[IMPORTANT]
===========
It is crucial that _every_ monitor operation has a different interval!
This is because Pacemaker currently differentiates between operations
only by resource and interval; so if eg. a master/slave resource has
the same monitor interval for both roles, Pacemaker would ignore the
role when checking the status - which would cause unexpected return
codes, and therefore unnecessary complications.
===========
.Monitoring both states of a multi-state resource
======
[source,XML]
-------
<master id="myMasterRsc">
<primitive id="myRsc" class="ocf" type="myApp" provider="myCorp">
<operations>
<op id="public-ip-slave-check" name="monitor" interval="60"/>
<op id="public-ip-master-check" name="monitor" interval="61" role="Master"/>
</operations>
</primitive>
</master>
-------
======
=== Multi-state Constraints ===
In most cases, a multi-state resources will have a single copy on each
active cluster node. If this is not the case, you can indicate which
nodes the cluster should preferentially assign copies to with resource
location constraints. These constraints are written no differently to
those for regular resources except that the master's id is used.
When considering multi-state resources in constraints, for most
purposes it is sufficient to treat them as clones. The exception is
when the +rsc-role+ and/or +with-rsc-role+ fields (for colocation
constraints) and +first-action+ and/or +then-action+ fields (for
ordering constraints) are used.
.Additional constraint options relevant to multi-state resources
[width="95%",cols="3m,5<",options="header",align="center"]
|=========================================================
|Field
|Description
|rsc-role
|An additional attribute of colocation constraints that specifies the
role that +rsc+ must be in. Allowed values: _Started_, +Master+,
+Slave+.
indexterm:[rsc-role,Ordering Constraints]
indexterm:[Constraints,Ordering,rsc-role]
|with-rsc-role
|An additional attribute of colocation constraints that specifies the
role that +with-rsc+ must be in. Allowed values: _Started_,
+Master+, +Slave+.
indexterm:[with-rsc-role,Ordering Constraints]
indexterm:[Constraints,Ordering,with-rsc-role]
|first-action
|An additional attribute of ordering constraints that specifies the
action that the +first+ resource must complete before executing the
specified action for the +then+ resource. Allowed values: _start_,
+stop+, +promote+, +demote+.
indexterm:[first-action,Ordering Constraints]
indexterm:[Constraints,Ordering,first-action]
|then-action
|An additional attribute of ordering constraints that specifies the
action that the +then+ resource can only execute after the
+first-action+ on the +first+ resource has completed. Allowed
values: +start+, +stop+, +promote+, +demote+. Defaults to the value
(specified or implied) of +first-action+.
indexterm:[then-action,Ordering Constraints]
indexterm:[Constraints,Ordering,then-action]
|=========================================================
In the example below, +myApp+ will wait until one of the database
copies has been started and promoted to master before being started
itself. Only if no copies can be promoted will +apache-stats+ be
prevented from being active. Additionally, the database will wait for
+myApp+ to be stopped before it is demoted.
.Example constraints involving multi-state resources
======
[source,XML]
-------
<constraints>
<rsc_location id="db-prefers-node1" rsc="database" node="node1" score="500"/>
<rsc_colocation id="backup-with-db-slave" rsc="backup"
with-rsc="database" with-rsc-role="Slave"/>
<rsc_colocation id="myapp-with-db-master" rsc="myApp"
with-rsc="database" with-rsc-role="Master"/>
<rsc_order id="start-db-before-backup" first="database" then="backup"/>
<rsc_order id="promote-db-then-app" first="database" first-action="promote"
then="myApp" then-action="start"/>
</constraints>
-------
======
Colocation of a regular (or group) resource with a multi-state
resource means that it can run on any machine with an active copy of
the multi-state resource that is in the specified state (+Master+ or
+Slave+). In the example, the cluster will choose a location based on
where database is running as a +Master+, and if there are multiple
+Master+ instances it will also factor in +myApp+'s own location
preferences when deciding which location to choose.
Colocation with regular clones and other multi-state resources is also
possible. In such cases, the set of allowed locations for the +rsc+
clone is (after role filtering) limited to nodes on which the
+with-rsc+ multi-state resource is (or will be) in the specified role.
Allocation is then performed as-per-normal.
=== Multi-state Stickiness ===
indexterm:[resource-stickiness,Multi-State]
To achieve a stable allocation pattern, multi-state resources are
slightly sticky by default. If no value for +resource-stickiness+ is
provided, the multi-state resource will use a value of 1. Being a
small value, it causes minimal disturbance to the score calculations
of other resources but is enough to prevent Pacemaker from needlessly
moving copies around the cluster.
=== Which Resource Instance is Promoted ===
During the start operation, most Resource Agent scripts should call
the `crm_master` utility. This tool automatically detects both the
resource and host and should be used to set a preference for being
promoted. Based on this, +master-max+, and +master-node-max+, the
instance(s) with the highest preference will be promoted.
The other alternative is to create a location constraint that
indicates which nodes are most preferred as masters.
.Manually specifying which node should be promoted
======
[source,XML]
-------
<rsc_location id="master-location" rsc="myMasterRsc">
<rule id="master-rule" score="100" role="Master">
<expression id="master-exp" attribute="#uname" operation="eq" value="node1"/>
</rule>
</rsc_location>
-------
======
=== Multi-state Resource Agent Requirements ===
Since multi-state resources are an extension of cloned resources, all
the requirements of Clones are also requirements of multi-state
resources. Additionally, multi-state resources require two extra
actions: +demote+ and +promote+; these actions are responsible for
changing the state of the resource. Like +start+ and +stop+, they
should return +OCF_SUCCESS+ if they completed successfully or a
relevant error code if they did not.
The states can mean whatever you wish, but when the resource is
started, it must come up in the mode called +Slave+. From there the
cluster will then decide which instances to promote to +Master+.
In addition to the Clone requirements for monitor actions, agents must
also _accurately_ report which state they are in. The cluster relies
on the agent to report its status (including role) accurately and does
not indicate to the agent what role it currently believes it to be in.
.Role implications of OCF return codes
[width="95%",cols="5,3<",options="header",align="center"]
|=========================================================
|Monitor Return Code
|Description
|OCF_NOT_RUNNING
|Stopped
- indexterm:[return code,OCF_NOT_RUNNING]
+ indexterm:[Return Code,OCF_NOT_RUNNING]
|OCF_SUCCESS
|Running (Slave)
- indexterm:[return code,OCF_SUCCESS]
+ indexterm:[Return Code,OCF_SUCCESS]
|OCF_RUNNING_MASTER
|Running (Master)
- indexterm:[return code,OCF_RUNNING_MASTER]
+ indexterm:[Return Code,OCF_RUNNING_MASTER]
|OCF_FAILED_MASTER
|Failed (Master)
- indexterm:[return code,OCF_FAILED_MASTER]
+ indexterm:[Return Code,OCF_FAILED_MASTER]
|Other
|Failed (Slave)
|=========================================================
=== Multi-state Notifications ===
Like clones, supporting notifications requires the +notify+ action to
be implemented. Once supported the notify action will be passed a
number of extra variables which, when combined with additional
context, can be used to calculate the current state of the cluster and
what is about to happen to it.
.Environment variables supplied with Master notify actions footnote:[Emphasized variables are specific to +Master+ resources and all behave in the same manner as described for Clone resources.]
[width="95%",cols="5,3<",options="header",align="center"]
|=========================================================
|Variable
|Description
|OCF_RESKEY_CRM_meta_notify_type
|Allowed values: +pre+, +post+
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,type]
indexterm:[type,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_operation
|Allowed values: +start+, +stop+
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,operation]
indexterm:[operation,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_active_resource
|Resources the that are running
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,active_resource]
indexterm:[active_resource,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_inactive_resource
|Resources the that are not running
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,inactive_resource]
indexterm:[inactive_resource,Notification Environment Variable]
|_OCF_RESKEY_CRM_meta_notify_master_resource_
|Resources that are running in +Master+ mode
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,master_resource]
indexterm:[master_resource,Notification Environment Variable]
|_OCF_RESKEY_CRM_meta_notify_slave_resource_
|Resources that are running in +Slave+ mode
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,slave_resource]
indexterm:[slave_resource,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_start_resource
|Resources to be started
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,start_resource]
indexterm:[start_resource,Notification Environment Variable]
|indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,stop_resource]
indexterm:[stop_resource,Notification Environment Variable]
OCF_RESKEY_CRM_meta_notify_stop_resource
|Resources to be stopped
|_OCF_RESKEY_CRM_meta_notify_promote_resource_
|Resources to be promoted
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,promote_resource]
indexterm:[promote_resource,Notification Environment Variable]
|_OCF_RESKEY_CRM_meta_notify_demote_resource_
|Resources to be demoted
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,demote_resource]
indexterm:[demote_resource,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_start_uname
|Nodes on which resources will be started
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,start_uname]
indexterm:[start_uname,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_stop_uname
|Nodes on which resources will be stopped
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,stop_uname]
indexterm:[stop_uname,Notification Environment Variable]
|_OCF_RESKEY_CRM_meta_notify_promote_uname_
|Nodes on which resources will be promote
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,promote_uname]
indexterm:[promote_uname,Notification Environment Variable]
|_OCF_RESKEY_CRM_meta_notify_demote_uname_
|Nodes on which resources will be demoted
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,demote_uname]
indexterm:[demote_uname,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_active_uname
|Nodes on which resources are running
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,active_uname]
indexterm:[active_uname,Notification Environment Variable]
|OCF_RESKEY_CRM_meta_notify_inactive_uname
|Nodes on which resources are not running
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,inactive_uname]
indexterm:[inactive_uname,Notification Environment Variable]
|_OCF_RESKEY_CRM_meta_notify_master_uname_
|Nodes on which resources are running in +Master+ mode
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,master_uname]
indexterm:[master_uname,Notification Environment Variable]
|_OCF_RESKEY_CRM_meta_notify_slave_uname_
|Nodes on which resources are running in +Slave+ mode
indexterm:[Environment Variable,OCF_RESKEY_CRM_meta_notify_,slave_uname]
indexterm:[slave_uname,Notification Environment Variable]
|=========================================================
=== Multi-state - Proper Interpretation of Notification Environment Variables ===
.Pre-notification (demote):
* +Active+ resources: +$OCF_RESKEY_CRM_meta_notify_active_resource+
* +Master+ resources: +$OCF_RESKEY_CRM_meta_notify_master_resource+
* +Slave+ resources: +$OCF_RESKEY_CRM_meta_notify_slave_resource+
* Inactive resources: +$OCF_RESKEY_CRM_meta_notify_inactive_resource+
* Resources to be started: +$OCF_RESKEY_CRM_meta_notify_start_resource+
* Resources to be promoted: +$OCF_RESKEY_CRM_meta_notify_promote_resource+
* Resources to be demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+
* Resources to be stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+
.Post-notification (demote) / Pre-notification (stop):
* +Active+ resources: +$OCF_RESKEY_CRM_meta_notify_active_resource+
* +Master+ resources:
** +$OCF_RESKEY_CRM_meta_notify_master_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_demote_resource+
* +Slave+ resources: +$OCF_RESKEY_CRM_meta_notify_slave_resource+
* Inactive resources: +$OCF_RESKEY_CRM_meta_notify_inactive_resource+
* Resources to be started: +$OCF_RESKEY_CRM_meta_notify_start_resource+
* Resources to be promoted: +$OCF_RESKEY_CRM_meta_notify_promote_resource+
* Resources to be demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+
* Resources to be stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+
* Resources that were demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+
.Post-notification (stop) / Pre-notification (start)
* +Active+ resources:
** +$OCF_RESKEY_CRM_meta_notify_active_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+
* +Master+ resources:
** +$OCF_RESKEY_CRM_meta_notify_master_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_demote_resource+
* +Slave+ resources:
** +$OCF_RESKEY_CRM_meta_notify_slave_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+
* Inactive resources:
** +$OCF_RESKEY_CRM_meta_notify_inactive_resource+
** plus +$OCF_RESKEY_CRM_meta_notify_stop_resource+
* Resources to be started: +$OCF_RESKEY_CRM_meta_notify_start_resource+
* Resources to be promoted: +$OCF_RESKEY_CRM_meta_notify_promote_resource+
* Resources to be demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+
* Resources to be stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+
* Resources that were demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+
* Resources that were stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+
.Post-notification (start) / Pre-notification (promote)
* +Active+ resources:
** +$OCF_RESKEY_CRM_meta_notify_active_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+
** plus +$OCF_RESKEY_CRM_meta_notify_start_resource+
* +Master+ resources:
** +$OCF_RESKEY_CRM_meta_notify_master_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_demote_resource+
* +Slave+ resources:
** +$OCF_RESKEY_CRM_meta_notify_slave_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+
** plus +$OCF_RESKEY_CRM_meta_notify_start_resource+
* Inactive resources:
** +$OCF_RESKEY_CRM_meta_notify_inactive_resource+
** plus +$OCF_RESKEY_CRM_meta_notify_stop_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_start_resource+
* Resources to be started: +$OCF_RESKEY_CRM_meta_notify_start_resource+
* Resources to be promoted: +$OCF_RESKEY_CRM_meta_notify_promote_resource+
* Resources to be demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+
* Resources to be stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+
* Resources that were started: +$OCF_RESKEY_CRM_meta_notify_start_resource+
* Resources that were demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+
* Resources that were stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+
.Post-notification (promote)
* +Active+ resources:
** +$OCF_RESKEY_CRM_meta_notify_active_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+
** plus +$OCF_RESKEY_CRM_meta_notify_start_resource+
* +Master+ resources:
** +$OCF_RESKEY_CRM_meta_notify_master_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_demote_resource+
** plus +$OCF_RESKEY_CRM_meta_notify_promote_resource+
* +Slave+ resources:
** +$OCF_RESKEY_CRM_meta_notify_slave_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_stop_resource+
** plus +$OCF_RESKEY_CRM_meta_notify_start_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_promote_resource+
* Inactive resources:
** +$OCF_RESKEY_CRM_meta_notify_inactive_resource+
** plus +$OCF_RESKEY_CRM_meta_notify_stop_resource+
** minus +$OCF_RESKEY_CRM_meta_notify_start_resource+
* Resources to be started: +$OCF_RESKEY_CRM_meta_notify_start_resource+
* Resources to be promoted: +$OCF_RESKEY_CRM_meta_notify_promote_resource+
* Resources to be demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+
* Resources to be stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+
* Resources that were started: +$OCF_RESKEY_CRM_meta_notify_start_resource+
* Resources that were promoted: +$OCF_RESKEY_CRM_meta_notify_promote_resource+
* Resources that were demoted: +$OCF_RESKEY_CRM_meta_notify_demote_resource+
* Resources that were stopped: +$OCF_RESKEY_CRM_meta_notify_stop_resource+
diff --git a/doc/Pacemaker_Explained/en-US/Ch-Basics.txt b/doc/Pacemaker_Explained/en-US/Ch-Basics.txt
index 8f4bfa14d6..63681c64f2 100644
--- a/doc/Pacemaker_Explained/en-US/Ch-Basics.txt
+++ b/doc/Pacemaker_Explained/en-US/Ch-Basics.txt
@@ -1,368 +1,368 @@
= Configuration Basics =
== Configuration Layout ==
The cluster is written using XML notation and divided into two main
sections: configuration and status.
The status section contains the history of each resource on each node
and based on this data, the cluster can construct the complete current
state of the cluster. The authoritative source for the status section
is the local resource manager (lrmd) process on each cluster node and
the cluster will occasionally repopulate the entire section. For this
reason it is never written to disk and administrators are advised
against modifying it in any way.
The configuration section contains the more traditional information
like cluster options, lists of resources and indications of where they
should be placed. The configuration section is the primary focus of
this document.
The configuration section itself is divided into four parts:
* Configuration options (called +crm_config+)
* Nodes
* Resources
* Resource relationships (called +constraints+)
.An empty configuration
======
[source,XML]
-------
<cib admin_epoch="0" epoch="0" num_updates="0" have-quorum="false">
<configuration>
<crm_config/>
<nodes/>
<resources/>
<constraints/>
</configuration>
<status/>
</cib>
-------
======
== The Current State of the Cluster ==
Before one starts to configure a cluster, it is worth explaining how
to view the finished product. For this purpose we have created the
`crm_mon` utility that will display the
current state of an active cluster. It can show the cluster status by
node or by resource and can be used in either single-shot or
dynamically-updating mode. There are also modes for displaying a list
of the operations performed (grouped by node and resource) as well as
information about failures.
Using this tool, you can examine the state of the cluster for
irregularities and see how it responds when you cause or simulate
failures.
Details on all the available options can be obtained using the
`crm_mon --help` command.
.Sample output from crm_mon
======
-------
============
Last updated: Fri Nov 23 15:26:13 2007
Current DC: sles-3 (2298606a-6a8c-499a-9d25-76242f7006ec)
3 Nodes configured.
5 Resources configured.
============
Node: sles-1 (1186dc9a-324d-425a-966e-d757e693dc86): online
192.168.100.181 (heartbeat::ocf:IPaddr): Started sles-1
192.168.100.182 (heartbeat:IPaddr): Started sles-1
192.168.100.183 (heartbeat::ocf:IPaddr): Started sles-1
rsc_sles-1 (heartbeat::ocf:IPaddr): Started sles-1
child_DoFencing:2 (stonith:external/vmware): Started sles-1
Node: sles-2 (02fb99a8-e30e-482f-b3ad-0fb3ce27d088): standby
Node: sles-3 (2298606a-6a8c-499a-9d25-76242f7006ec): online
rsc_sles-2 (heartbeat::ocf:IPaddr): Started sles-3
rsc_sles-3 (heartbeat::ocf:IPaddr): Started sles-3
child_DoFencing:0 (stonith:external/vmware): Started sles-3
-------
======
.Sample output from crm_mon -n
======
-------
============
Last updated: Fri Nov 23 15:26:13 2007
Current DC: sles-3 (2298606a-6a8c-499a-9d25-76242f7006ec)
3 Nodes configured.
5 Resources configured.
============
Node: sles-1 (1186dc9a-324d-425a-966e-d757e693dc86): online
Node: sles-2 (02fb99a8-e30e-482f-b3ad-0fb3ce27d088): standby
Node: sles-3 (2298606a-6a8c-499a-9d25-76242f7006ec): online
Resource Group: group-1
192.168.100.181 (heartbeat::ocf:IPaddr): Started sles-1
192.168.100.182 (heartbeat:IPaddr): Started sles-1
192.168.100.183 (heartbeat::ocf:IPaddr): Started sles-1
rsc_sles-1 (heartbeat::ocf:IPaddr): Started sles-1
rsc_sles-2 (heartbeat::ocf:IPaddr): Started sles-3
rsc_sles-3 (heartbeat::ocf:IPaddr): Started sles-3
Clone Set: DoFencing
child_DoFencing:0 (stonith:external/vmware): Started sles-3
child_DoFencing:1 (stonith:external/vmware): Stopped
child_DoFencing:2 (stonith:external/vmware): Started sles-1
-------
======
The DC (Designated Controller) node is where all the decisions are
made and if the current DC fails a new one is elected from the
remaining cluster nodes. The choice of DC is of no significance to an
administrator beyond the fact that its logs will generally be more
interesting.
== How Should the Configuration be Updated? ==
There are three basic rules for updating the cluster configuration:
* Rule 1 - Never edit the cib.xml file manually. Ever. I'm not making this up.
* Rule 2 - Read Rule 1 again.
* Rule 3 - The cluster will notice if you ignored rules 1 &amp; 2 and refuse to use the configuration.
Now that it is clear how NOT to update the configuration, we can begin
to explain how you should.
The most powerful tool for modifying the configuration is the
+cibadmin+ command which talks to a running cluster. With +cibadmin+,
the user can query, add, remove, update or replace any part of the
configuration; all changes take effect immediately, so there is no
need to perform a reload-like operation.
The simplest way of using cibadmin is to use it to save the current
configuration to a temporary file, edit that file with your favorite
text or XML editor and then upload the revised configuration.
.Safely using an editor to modify the cluster configuration
======
[source,C]
--------
# cibadmin --query > tmp.xml
# vi tmp.xml
# cibadmin --replace --xml-file tmp.xml
--------
======
Some of the better XML editors can make use of a Relax NG schema to
help make sure any changes you make are valid. The schema describing
the configuration can normally be found in
-pass:[<filename>/usr/lib/heartbeat/pacemaker.rng</filename>] on most
-systems.
+'/usr/lib/heartbeat/pacemaker.rng' on most systems.
If you only wanted to modify the resources section, you could instead
do
.Safely using an editor to modify a subsection of the cluster configuration
======
[source,C]
--------
# cibadmin --query --obj_type resources > tmp.xml
# vi tmp.xml
# cibadmin --replace --obj_type resources --xml-file tmp.xml
--------
======
to avoid modifying any other part of the configuration.
== Quickly Deleting Part of the Configuration ==
Identify the object you wish to delete. Eg. run
.Searching for STONITH related configuration items
======
[source,C]
---------
# cibadmin -Q | grep stonith
- <nvpair id="cib-bootstrap-options-stonith-action" name="stonith-action" value="reboot"/>
- <nvpair id="cib-bootstrap-options-stonith-enabled" name="stonith-enabled" value="1"/>
- <primitive id="child_DoFencing" class="stonith" type="external/vmware">
- <lrm_resource id="child_DoFencing:0" type="external/vmware" class="stonith">
- <lrm_resource id="child_DoFencing:0" type="external/vmware" class="stonith">
- <lrm_resource id="child_DoFencing:1" type="external/vmware" class="stonith">
- <lrm_resource id="child_DoFencing:0" type="external/vmware" class="stonith">
- <lrm_resource id="child_DoFencing:2" type="external/vmware" class="stonith">
- <lrm_resource id="child_DoFencing:0" type="external/vmware" class="stonith">
- <lrm_resource id="child_DoFencing:3" type="external/vmware" class="stonith">
+[source,XML]
+--------
+ <nvpair id="cib-bootstrap-options-stonith-action" name="stonith-action" value="reboot"/>
+ <nvpair id="cib-bootstrap-options-stonith-enabled" name="stonith-enabled" value="1"/>
+ <primitive id="child_DoFencing" class="stonith" type="external/vmware">
+ <lrm_resource id="child_DoFencing:0" type="external/vmware" class="stonith">
+ <lrm_resource id="child_DoFencing:0" type="external/vmware" class="stonith">
+ <lrm_resource id="child_DoFencing:1" type="external/vmware" class="stonith">
+ <lrm_resource id="child_DoFencing:0" type="external/vmware" class="stonith">
+ <lrm_resource id="child_DoFencing:2" type="external/vmware" class="stonith">
+ <lrm_resource id="child_DoFencing:0" type="external/vmware" class="stonith">
+ <lrm_resource id="child_DoFencing:3" type="external/vmware" class="stonith">
--------
======
Next identify the resource's tag name and id (in this case we'll
choose +primitive+ and +child_DoFencing+). Then simply execute:
-
-`cibadmin --delete --crm_xml '&lt;primitive id="child_DoFencing"/>'`
+[source,C]
+# cibadmin --delete --crm_xml '&lt;primitive id="child_DoFencing"/>'
== Updating the Configuration Without Using XML ==
Some common tasks can also be performed with one of the higher level
tools that avoid the need to read or edit XML.
To enable stonith for example, one could run:
[source,C]
# crm_attribute --attr-name stonith-enabled --attr-value true
Or, to see if +somenode+ is allowed to run resources, there is:
[source,C]
# crm_standby --get-value --node-uname somenode
Or, to find the current location of +my-test-rsc+, one can use:
[source,C]
# crm_resource --locate --resource my-test-rsc
[[s-config-sandboxes]]
== Making Configuration Changes in a Sandbox ==
Often it is desirable to preview the effects of a series of changes
before updating the configuration atomically. For this purpose we
have created `crm_shadow` which creates a
"shadow" copy of the configuration and arranges for all the command
line tools to use it.
To begin, simply invoke `crm_shadow` and give
it the name of a configuration to create footnote:[Shadow copies are
identified with a name, making it possible to have more than one.] ;
be sure to follow the simple on-screen instructions.
WARNING: Read the above carefully, failure to do so could result in you
destroying the cluster's active configuration!
.Creating and displaying the active sandbox
[source,Bash]
======
--------
# crm_shadow --create test
Setting up shadow instance
Type Ctrl-D to exit the crm_shadow shell
shadow[test]:
shadow[test] # crm_shadow --which
test
--------
======
From this point on, all cluster commands will automatically use the
shadow copy instead of talking to the cluster's active configuration.
Once you have finished experimenting, you can either commit the
changes, or discard them as shown below. Again, be sure to follow the
on-screen instructions carefully.
For a full list of `crm_shadow` options and
commands, invoke it with the <parameter>--help</parameter> option.
.Using a sandbox to make multiple changes atomically
======
[source,Bash]
--------
shadow[test] # crm_failcount -G -r rsc_c001n01
name=fail-count-rsc_c001n01 value=0
shadow[test] # crm_standby -v on -n c001n02
shadow[test] # crm_standby -G -n c001n02
name=c001n02 scope=nodes value=on
shadow[test] # cibadmin --erase --force
shadow[test] # cibadmin --query
<cib cib_feature_revision="1" validate-with="pacemaker-1.0" admin_epoch="0" crm_feature_set="3.0" have-quorum="1" epoch="112"
dc-uuid="c001n01" num_updates="1" cib-last-written="Fri Jun 27 12:17:10 2008">
<configuration>
<crm_config/>
<nodes/>
<resources/>
<constraints/>
</configuration>
<status/>
</cib>
shadow[test] # crm_shadow --delete test --force
Now type Ctrl-D to exit the crm_shadow shell
shadow[test] # exit
# crm_shadow --which
No shadow instance provided
# cibadmin -Q
<cib cib_feature_revision="1" validate-with="pacemaker-1.0" admin_epoch="0" crm_feature_set="3.0" have-quorum="1" epoch="110"
dc-uuid="c001n01" num_updates="551">
<configuration>
<crm_config>
<cluster_property_set id="cib-bootstrap-options">
<nvpair id="cib-bootstrap-1" name="stonith-enabled" value="1"/>
<nvpair id="cib-bootstrap-2" name="pe-input-series-max" value="30000"/>
--------
======
Making changes in a sandbox and verifying the real configuration is untouched
[[s-config-testing-changes]]
== Testing Your Configuration Changes ==
We saw previously how to make a series of changes to a "shadow" copy
of the configuration. Before loading the changes back into the
cluster (eg. `crm_shadow --commit mytest --force`), it is often
advisable to simulate the effect of the changes with +crm_simulate+,
eg.
[source,C]
# crm_simulate --live-check -VVVVV --save-graph tmp.graph --save-dotfile tmp.dot
The tool uses the same library as the live cluster to show what it
would have done given the supplied input. It's output, in addition to
a significant amount of logging, is stored in two files +tmp.graph+
and +tmp.dot+, both are representations of the same thing -- the
cluster's response to your changes.
In the graph file is stored the complete transition, containing a list
of all the actions, their parameters and their pre-requisites.
Because the transition graph is not terribly easy to read, the tool
also generates a Graphviz dot-file representing the same information.
== Interpreting the Graphviz output ==
* Arrows indicate ordering dependencies
* Dashed-arrows indicate dependencies that are not present in the transition graph
* Actions with a dashed border of any color do not form part of the transition graph
* Actions with a green border form part of the transition graph
* Actions with a red border are ones the cluster would like to execute but cannot run
* Actions with a blue border are ones the cluster does not feel need to be executed
* Actions with orange text are pseudo/pretend actions that the cluster uses to simplify the graph
* Actions with black text are sent to the LRM
* Resource actions have text of the form pass:[<replaceable>rsc</replaceable>]_pass:[<replaceable>action</replaceable>]_pass:[<replaceable>interval</replaceable>] pass:[<replaceable>node</replaceable>]
* Any action depending on an action with a red border will not be able to execute.
* Loops are _really_ bad. Please report them to the development team.
=== Small Cluster Transition ===
image::images/Policy-Engine-small.png["An example transition graph as represented by Graphviz",width="16cm",height="6cm",align="center"]
In the above example, it appears that a new node, +node2+, has come
online and that the cluster is checking to make sure +rsc1+, +rsc2+
and +rsc3+ are not already running there (Indicated by the
+*_monitor_0+ entries). Once it did that, and assuming the resources
were not active there, it would have liked to stop +rsc1+ and +rsc2+
on +node1+ and move them to +node2+. However, there appears to be
some problem and the cluster cannot or is not permitted to perform the
stop actions which implies it also cannot perform the start actions.
For some reason the cluster does not want to start +rsc3+ anywhere.
For information on the options supported by `crm_simulate`, use
the `--help` option.
=== Complex Cluster Transition ===
image::images/Policy-Engine-big.png["Another, slightly more complex, transition graph that you're not expected to be able to read",width="16cm",height="20cm",align="center"]
== Do I Need to Update the Configuration on all Cluster Nodes? ==
No. Any changes are immediately synchronized to the other active
members of the cluster.
To reduce bandwidth, the cluster only broadcasts the incremental
updates that result from your changes and uses MD5 checksums to ensure
that each copy is completely consistent.

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