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Adding Constraints to High Availability Cluster Resources
SUSE Linux Enterprise High Availability 16.0

Adding Constraints to High Availability Cluster Resources

Publication Date: 13 Aug 2026

Resource constraints let you specify cluster node assignments, define the start order, and manage dependencies between resources. Because cluster resources sometimes depend on other resources or on a particular node configuration, they might need to run in a specific location or start in a specific order. Add resource constraints to specify exactly where and when High Availability cluster resources can run.

Requirements:

  • An existing SUSE Linux Enterprise High Availability cluster

  • Existing cluster resources

Tip

If you still need to configure cluster resources, see Configuring High Availability Cluster Resources.

1 What are cluster resources?

 

In a High Availability cluster, the applications and services that need to be highly available are called resources. Cluster resources can include Web sites, e-mail servers, databases, file systems, virtual machines or any other applications or services that need to be available to users at all times. You can start, stop, monitor and move resources as needed. You can also specify whether resources should run together on the same node, or start and stop in sequential order. If a node fails, the resources running on it fail over (move) to another node instead of being lost.

In SUSE Linux Enterprise High Availability, the cluster resource manager (CRM) is Pacemaker, which manages and coordinates all cluster services. Pacemaker uses resource agents (RAs) to start, stop and monitor resources. A resource agent abstracts the resource and presents its status to the cluster. This means that Pacemaker only interacts with the resource agent, not with the actual application or service. SUSE Linux Enterprise High Availability supports many different resource agents that are designed to manage specific types of resources.

1.1 Primitive resources

 

Primitive resources represent the applications or services that need to be highly available. Configuring a primitive specifies the resource agent and any other information required for the cluster to manage a resource. To see the supported resource agent classes, run crm ra classes. To see the resource agents available within a class, run crm ra list CLASS.

Primitive resources can have the following settings:

Properties

Resource properties are the basic details required by the cluster: a unique name for the resource, and the resource agent that manages the application or service.

Parameters

Parameters are specific to each resource agent and determine the details and behavior of an application or service. To show all the parameters available for a resource agent, run crm ra info RESOURCE_AGENT.

Operations

Operations are actions that the cluster can perform on a resource, such as start, stop and monitor. To show the supported operations for a resource agent, run crm ra info RESOURCE_AGENT and scroll to the bottom of the output.

Meta attributes

Meta attributes change how the cluster treats a resource. To show all the meta attributes available for primitives, run crm_resource --list-options primitive.

Utilization attributes

If the cluster nodes have utilization attributes configured, you can add these attributes to cluster resources to help with load balancing. For more information, see https://clusterlabs.org/projects/pacemaker/doc/3.0/Pacemaker_Explained/html/utilization.html.

1.2 Resource groups

 

Cluster resources might depend on other resources, such as a Web server that requires an IP address and a file system. You can combine these resources into a resource group. Groups contain multiple primitives that need to be located together, started sequentially and stopped in the reverse order.

This diagram shows a box representing a node. The box contains four individual resources and a smaller box containing three more resources. The smaller box represents a resource group. A zoomed-in view of the resource group shows that the resources are an IP address, an XFS file system and an Apache Web server. The resources are numbered to show the start order in one direction and the reversed stop order in the other direction.
Figure 1: Resource group
 

Groups have the following properties:

Contents

Groups can only contain primitive resources, not clones or other groups.

Starting and stopping

Resources start in the order they appear and stop in the reverse order.

Location

Resources in the group must all run on the same node.

Dependency

If one of the resources can't run anywhere, then the resources that appear after it in the group can't run anywhere either.

Meta attributes

The meta attributes target-role, priority, maintenance and is-managed can be added directly to the group. All other attributes are inherited from the group's resources.

Resource stickiness

Stickiness in groups is additive. Every active resource in the group contributes its stickiness value to the group's total.

1.3 Resource clones

 

Resource clones can run simultaneously on multiple nodes. This is required for cluster file systems like GFS2, for example. You can clone a primitive or a group if the resource agent supports it. Clones can also have additional clone-specific meta attributes to change their behavior.

Clones can be one of the following types:

Anonymous clones

Anonymous clones are the simplest type. All instances of the clone behave identically. Therefore, only one instance of an anonymous clone can be active on each node.

Globally unique clones

Globally unique clones are distinct entities. An instance of the clone running on one node is not necessarily equivalent to another instance on another node.

Promotable clones

Promotable clones allow the instances to be in one of two operating modes: promoted or unpromoted (also known as primary and secondary, or active and passive). Promotable clones can be either anonymous or globally unique.

To make a clone promotable, the resource agent must support the promote and demote operations. The cluster determines which instance of the clone to promote using one of the following methods (or a combination of both):

  • If a resource agent supports promotable clones, it might automatically set promotion scores based on its own preference for which instance to promote.

  • You can manually set promotion rules or preferences by creating location or colocation constraints.

For more information, see https://clusterlabs.org/projects/pacemaker/doc/3.0/Pacemaker_Explained/html/collective.html#determining-which-instance-is-promoted

1.4 For more information

 

2 What are resource constraints?

 

Resource constraints let you specify cluster node assignments, define the start order, and manage dependencies between resources.

2.1 Types of constraints

 
Order

Order constraints tell the cluster to start resources in a specific order and stop them in the reverse order. You can also start or stop a resource right before or after a different resource performs a certain action, such as being promoted.

Location

Location constraints tell the cluster where resources can or cannot run. You can specify that a resource must or must not run on a particular node, or give the resource an optional preference for or against a node.

Colocation

Colocation constraints tell the cluster which resources can or cannot run together on the same node. You can specify that the resources must or must not run together, or give a resource an optional preference for or against another resource.

Important
Important: Restrictions for constraints and primitive resources

  • Don't add colocation constraints to primitives in a resource group. Add a colocation constraint to the group instead.

  • Don't add any constraints to a primitive that has been cloned. Add constraints to the clone instead.

2.2 Scores and kinds

 

Location and colocation constraints must have a score to indicate how important the constraint is. A score of INFINITY (positive or negative) means that the constraint must be applied. The score can also be a non-infinite number (positive or negative), which means the constraint is only a preference. In this case, the constraint might not be applied if its score is outweighed by other factors, such as other constraints, resource stickiness, failure thresholds, etc.

For location constraints, a positive score means the resource should (or must) run on the specified node. A negative score means the resource should not (or must not) run on the specified node. You can also add multiple location constraints with different scores to prioritize node preferences.

For colocation constraints, a positive score means the resources should (or must) run together on the same node. A negative score means the resources should not (or must not) run together on the same node.

Instead of a score, order constraints must have a kind, which defines whether the constraint is mandatory or optional.

2.3 Resource sets

 

Resource sets let you group multiple resources in a single constraint instead of needing multiple constraints. The effect depends on the type of constraint:

  • In a location constraint, a resource set applies the constraint to multiple resources instead of just one, without creating any dependency between the resources.

    Location constraints use curly brackets to group the resources.

  • In an order constraint, a resource set gives multiple resources the same position in the order. For example, a simple order constraint says that res1 must start first, then res2, then res3. However, if you put res2 and res3 in a resource set, the constraint would say that res1 must start first, and then res2 and res3 can start in any order.

    Order constraints can use round brackets or square brackets to group the resources.

  • In a colocation constraint, a resource set gives multiple resources the same relationship to the next resource. For example, a simple colocation constraint says that res1 must run on the same node as res2, which must run on the same node as res3. However, if you put res1 and res2 in a resource set, the constraint would say that res1 and res2 must run on the same node as res3, but aren't otherwise dependent on each other.

    Colocation constraints can use round brackets or square brackets to group the resources.

The syntax for resource sets can be complex, so before using them in a production environment, we recommend testing them to make sure the resources behave as expected.

For more information about the syntax of resource sets and the difference between round and square brackets, run crm help Resourcesets.

2.4 For more information

 

3 Adding order constraints

 

Order constraints tell the cluster to start resources in a specific order and stop them in the reverse order. You can also start or stop a resource right before or after a different resource performs a certain action, such as being promoted.

Instead of a score, order constraints have a kind. The kind can be one of the following:

  • Mandatory: Resources must start in this order.

  • Optional: The start order is only a preference.

  • Serialize: A resource must finish starting before the next resource can begin starting. This is useful for resources that put a high load on the node during start-up, for example.

You can add order constraints with the CRM Shell (crmsh) or with the Hawk Web interface.

  • CRM Shell
  • Hawk

You can perform this procedure on any node in the cluster.

  1. Log in either as the root user or as a user with sudo privileges.

  2. Add an order constraint. The basic command requires a name, a kind, and at least two resources: 

    > sudo crm configure order ORDER_NAME KIND: RESOURCE1 RESOURCE2

    The KIND can be Mandatory, Optional or Serialize.

    Additional options
     
    Resource sets

    You can use round brackets or square brackets to group resources in an order constraint. In this example, res1 must start first, and then res2 and res3 can start in any order: 

    > sudo crm configure order res1-first Mandatory: res1 [ res2 res3 ]

    Round brackets are treated as special characters in most shells, so for crm commands that aren't in interactive mode, you must escape the brackets with \: 

    > sudo crm configure order res1-first Mandatory: res1 \( res2 res3 \)

    For more information about the difference between round and square brackets, run crm help Resourcesets.

    Symmetry

    In most cases, you should keep the default symmetrical=true, which means that resources stop in the reverse of their start order. However, if necessary, you can change it to false.

    Actions

    You can require a resource to perform an action (start, stop, promote or demote) before or after another resource starts. In this example, res1 must start before clone2 can be promoted: 

    > sudo crm configure order res1-pr-clone2 Mandatory: res1 clone2:promote

  3. You can view all order constraints with the following command: 

    > sudo crm configure show type:order
For more information
 

4 Adding location constraints

 

Location constraints tell the cluster where resources can or cannot run. You can specify that a resource must or must not run on a particular node, or give the resource an optional preference for or against a node.

Location constraints use a score to indicate how important the constraint is. A score of INFINITY (positive or negative) means that the constraint must be applied. The score can also be a non-infinite number (positive or negative), which means the constraint is only a preference. You can also add multiple location constraints with different scores to prioritize node preferences.

You can add location constraints with the CRM Shell (crmsh) or with the Hawk Web interface.

  • CRM Shell
  • Hawk

You can perform this procedure on any node in the cluster.

  1. Log in either as the root user or as a user with sudo privileges.

  2. Add a location constraint. The basic command requires a name, at least one resource, a score, and a node: 

    > sudo crm configure location LOCATION_NAME RESOURCE SCORE: NODE

    The SCORE can be inf, -inf or a number (positive or negative).

    Additional options
     
    Resource sets

    You can use curly brackets to include multiple resources in a location constraint. In this example, res1 and res2 must both run on node alice: 

    > sudo crm configure location res1-2-alice { res1 res2 } inf: alice
    Resource patterns

    You can use a resource pattern (a regular expression between two slashes) to refer to multiple resources. If you add new resources with the same name pattern, they will also be included in the location constraint. In this example, any resources beginning with res must run on node alice: 

    > sudo crm configure location all-res-alice /res.*/ inf: alice
    Resource discovery

    In most cases, you should keep the default resource-discovery=always. This means that the cluster checks whether the resource is already running, to help avoid unwanted instances of the resource. However, if necessary, you can change it to never or exclusive.

    Rules

    Instead of specifying a single node, you can use a rule to refer to multiple nodes. If you add more nodes that meet the rule, they will also be included in the location constraint. In this example, res1 can't run on any node where the custom node attribute memory is less than 4096: 

    > sudo crm configure location res1-no-small-nodes res1 \
  rule -inf: memory lt 4096

  3. Check the status to see which node the resources are now running on: 

    > sudo crm status
For more information
 

5 Adding colocation constraints

 

Colocation constraints tell the cluster which resources can or cannot run together on the same node. You can specify that the resources must or must not run together, or give a resource an optional preference for or against another resource.

Colocation constraints use a score to indicate how important the constraint is. A score of INFINITY (positive or negative) means that the constraint must be applied. The score can also be a non-infinite number (positive or negative), which means the constraint is only a preference.

Important
Important: Resource start order

Colocation constraints don't affect the order in which the resources start. If you want resources to run on the same node and start in a specific order, create a resource group.

You can add colocation constraints with the CRM Shell (crmsh) or with the Hawk Web interface.

  • CRM Shell
  • Hawk

You can perform this procedure on any node in the cluster.

  1. Log in either as the root user or as a user with sudo privileges.

  2. Add a colocation constraint. The basic command requires a name, a score and at least two resources: 

    > sudo crm configure colocation COLOCATION_NAME SCORE: RESOURCE1 RESOURCE2

    The SCORE can be inf, -inf or a number (positive or negative).

    RESOURCE2 is assigned to a node first, and RESOURCE1 is placed relative to RESOURCE2.

    Additional options
     
    Resource sets

    You can use round brackets or square brackets to group resources in a colocation constraint. In this example, res1 and res2 must run on the same node as res3, but aren't otherwise dependent on each other: 

    > sudo crm configure colocation res1-2-with-res3 \
  inf: [ res1 res2 ] res3

    Round brackets are treated as special characters in most shells, so for crm commands that aren't in interactive mode, you must escape the brackets with \: 

    > sudo crm configure colocation res1-2-with-res3 \
  inf: \( res1 res2 \) res3

    For more information about the difference between round and square brackets, run crm help Resourcesets.

    Roles

    You can require a role (Started, Stopped, Promoted or Unpromoted) for one or more resources. The colocation constraint only applies when the resource is in this role. In this example, res1 must run on the same node where clone2 is in the Promoted role: 

    > sudo crm configure colocation res1-with-pr-clone2 \
  inf: res1 clone2:Promoted
    Node attributes

    You can use a node attribute to colocate resources on a group of nodes instead of one node. In this example, res1 and res2 don't have to run on the same node, but must run on nodes with the same value for the datacenter node attribute: 

    > sudo crm configure colocation res1-2-same-dc \
  inf: res1 res2 node-attribute=datacenter

  3. Check the status to see which node the resources are now running on: 

    > sudo crm status
For more information
 

6 Colocating resources without adding dependency

 

A colocation constraint creates dependency between the resources. If one resource fails, the cluster also restarts the other resource. However, sometimes you might need to place resources together without any dependency. You can do this with the CRM Shell's weak-bond command. This creates a Dummy resource, then creates a colocation constraint between the Dummy resource and the resources you specify.

You can perform this procedure on any node in the cluster.

  1. Log in either as the root user or as a user with sudo privileges.

  2. Run the following command, specifying two or more primitive resources: 

    > sudo crm configure assist weak-bond RESOURCE1 RESOURCE2
Create weak bond / independent colocation
The following elements will be created:
   * Colocation constraint, ID: place-constraint-1
   * Dummy resource, ID: place-dummy-1
Create resources (y/n)?

  3. Enter y to create the Dummy resource and colocation constraint.

  4. View the new constraint: 

    > sudo crm configure show place-constraint-1

  5. Check which node the resources are running on: 

    > sudo crm status
For more information
 

  • crm assist weak-bond --help

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HA glossary

 
active/active, active/passive

How resources run on the nodes. Active/passive means that resources only run on the active node, but can move to the passive node if the active node fails. Active/active means that all nodes are active at once, and resources can run on (and move to) any node in the cluster.

arbitrator

An arbitrator is a machine running outside the cluster to provide an additional instance for cluster calculations. For example, QNetd provides a vote to help QDevice participate in quorum decisions.

CIB (cluster information base)

An XML representation of the whole cluster configuration and status (cluster options, nodes, resources, constraints, etc.). The CIB manager (pacemaker-based) keeps the CIB synchronized across the cluster nodes and handles requests to modify it.

clone

In the context of a cluster resource, a clone is a resource that can be active on multiple nodes. Any resource can be cloned if its resource agent supports it.

cluster

A high-availability cluster is a group of servers (physical or virtual) designed primarily to secure the highest possible availability of data, applications and services. Not to be confused with a high-performance cluster, which shares the application load to achieve faster results.

Cluster LVM (Cluster logical volume manager)

The term Cluster LVM indicates that LVM is being used in a cluster environment. This requires configuration adjustments to protect the LVM metadata on shared storage.

cluster offline upgrade

If a new product version includes major changes that are backward incompatible, the cluster requires a cluster offline upgrade. You must stop the cluster services on all nodes and upgrade the whole cluster before bringing the nodes back online.

For minor version upgrades, see cluster rolling upgrade.

cluster partition

A cluster partition occurs when communication fails between one or more nodes and the rest of the cluster. The nodes are split into partitions but are still active. They can only communicate with nodes in the same partition and are unaware of the separated nodes. This is known as a split brain scenario.

cluster rolling upgrade

In a cluster rolling upgrade, one cluster node at a time is upgraded while the rest of the cluster is still running. Stop the cluster services on a node, upgrade it, then bring it back online to join the cluster. Continue one by one until all cluster nodes are upgraded.

For major version upgrades, see cluster offline upgrade.

cluster services

The services that run the cluster. Typically this refers to Pacemaker and Corosync, but might also include SBD and QDevice if those services are used.

cluster stack

The ensemble of software technologies and components that make up a cluster.

colocation constraint

A type of resource constraint that specifies which resources can or cannot run together on a node.

concurrency violation

A resource that should be running on only one node in the cluster is running on several nodes.

Corosync

Corosync provides reliable messaging, membership and quorum information about the cluster. This is handled by the Corosync Cluster Engine, a group communication system.

CRM (cluster resource manager)

The management entity responsible for coordinating all non-local interactions in a High Availability cluster. SUSE Linux Enterprise High Availability uses Pacemaker as the CRM. It interacts with several components: local executors on its own node and on the other nodes, non-local CRMs, administrative commands, the fencing functionality, and the membership layer.

crmsh (CRM Shell)

The command-line utility crmsh manages the cluster, nodes and resources.

Csync2

A synchronization tool for replicating configuration files across all nodes in the cluster.

DC (designated coordinator)

The pacemaker-controld daemon is the cluster controller, which coordinates all actions. This daemon has an instance on each cluster node, but only one instance is elected to act as the DC. The DC is elected when the cluster services start, or if the current DC fails or leaves the cluster. The DC decides whether a cluster-wide change must be performed, such as fencing a node or moving resources.

disaster

An unexpected interruption of critical infrastructure caused by nature, humans, hardware failure, or software bugs.

disaster recovery

The process by which a function is restored to the normal, steady state after a disaster.

Disaster Recovery Plan

A strategy to recover from a disaster with the minimum impact on IT infrastructure.

DLM (Distributed Lock Manager)

DLM coordinates accesses to shared resources in a cluster, for example, managing file locking in clustered file systems to increase performance and availability.

DRBD

DRBD® is a block device designed for building High Availability clusters. It replicates data on a primary device to secondary devices in a way that ensures all copies of the data remain identical.

existing cluster

The term existing cluster is used to refer to any cluster that consists of at least one node. An existing cluster has a basic Corosync configuration that defines the communication channels, but does not necessarily have resource configuration yet.

failover

Occurs when a resource or node fails on one machine and the affected resources move to another node.

failover domain

A named subset of cluster nodes that are eligible to run a resource if a node fails.

fencing

Prevents access to a shared resource by isolated or failing cluster members. There are two classes of fencing: resource-level fencing and node-level fencing. Resource-level fencing ensures exclusive access to a resource. Node-level fencing prevents a failed node from accessing shared resources and prevents resources from running on a node with an uncertain status. This is usually done by resetting or powering off the node.

GFS2

Global File System 2 (GFS2) is a shared disk file system for Linux computer clusters. GFS2 allows all nodes to have direct concurrent access to the same shared block storage. GFS2 has no disconnected operating mode, and no client or server roles. All nodes in a GFS2 cluster function as peers. GFS2 supports up to 32 cluster nodes. Using GFS2 in a cluster requires hardware to allow access to the shared storage, and a lock manager to control access to the storage.

group

Resource groups contain multiple resources that need to be located together, started sequentially and stopped in the reverse order.

Hawk (HA Web Konsole)

A user-friendly Web-based interface for monitoring and administering a High Availability cluster from Linux or non-Linux machines. Hawk can be accessed from any machine that can connect to the cluster nodes, using a graphical Web browser.

heuristics

QDevice supports using a set of commands (heuristics) that run locally on start-up of cluster services, cluster membership change, successful connection to the QNetd server, or optionally at regular times. The result is used in calculations to determine which partition should have quorum.

knet (kronosnet)

A network abstraction layer supporting redundancy, security, fault tolerance, and fast fail-over of network links. In SUSE Linux Enterprise High Availability 16, knet is the default transport protocol for the Corosync communication channels.

local cluster

A single cluster in one location (for example, all nodes are located in one data center). Network latency is minimal. Storage is typically accessed synchronously by all nodes.

local executor

The local executor is located between Pacemaker and the resources on each node. Through the pacemaker-execd daemon, Pacemaker can start, stop and monitor resources.

location

In the context of a whole cluster, location can refer to the physical location of nodes (for example, all nodes might be located in the same data center). In the context of a location constraint, location refers to the nodes on which a resource can or cannot run.

location constraint

A type of resource constraint that defines the nodes on which a resource can or cannot run.

meta attribute

Parameters that tell the CRM (cluster resource manager) how to treat a specific resource. For example, you might define a resource's priority or target role.

metro cluster

A single cluster that can stretch over multiple buildings or data centers, with all sites connected by Fibre Channel. Network latency is usually low. Storage is frequently replicated using mirroring or synchronous replication.

network device bonding

Network device bonding combines two or more network interfaces into a single bonded device to increase bandwidth and/or provide redundancy. When using Corosync, the bonded device is not managed by the cluster software. Therefore, the bonded device must be configured on every cluster node that might need to access it.

node

Any server (physical or virtual) that is a member of a cluster.

order constraint

A type of resource constraint that defines the sequence of actions.

Pacemaker

Pacemaker is the CRM (cluster resource manager) in SUSE Linux Enterprise High Availability, or the “brain” that reacts to events occurring in the cluster. Events might be nodes that join or leave the cluster, failure of resources, or scheduled activities such as maintenance, for example. The pacemakerd daemon launches and monitors all other related daemons.

parameters (instance attributes)

Parameters determine which instance of a service the resource controls.

primitive

A primitive resource is the most basic type of cluster resource.

promotable clone

Promotable clones are a special type of clone resource that can be promoted. Active instances of these resources are divided into two states: promoted and unpromoted (also known as “active and passive” or “primary and secondary”).

QDevice

QDevice and QNetd participate in quorum decisions. The corosync-qdevice daemon runs on each cluster node and communicates with QNetd to provide a configurable number of votes, allowing a cluster to sustain more node failures than the standard quorum rules allow.

QNetd

QNetd is an arbitrator that runs outside the cluster. The corosync-qnetd daemon provides a vote to the corosync-qdevice daemon on each node to help it participate in quorum decisions.

quorum

A cluster partition is defined to have quorum (be quorate) if it has the majority of nodes (or “votes”). Quorum distinguishes exactly one partition. This is part of the algorithm to prevent several disconnected partitions or nodes (“split brain”) from proceeding and causing data and service corruption. Quorum is a prerequisite for fencing, which then ensures that quorum is unique.

RA (resource agent)

A script acting as a proxy to manage a resource (for example, to start, stop or monitor a resource). SUSE Linux Enterprise High Availability supports different kinds of resource agents.

ReaR (Relax and Recover)

An administrator tool set for creating disaster recovery images.

resource

Any type of service or application that is known to Pacemaker, for example, an IP address, a file system, or a database. The term resource is also used for DRBD, where it names a set of block devices that use a common connection for replication.

resource constraint

Resource constraints specify which cluster nodes a resource can run on, what order the resources should start in, and which other resources a specific resource is dependent on.

See also colocation constraint, location constraint and order constraint.

resource set

As an alternative format for defining location, colocation or order constraints, you can use resource sets, where primitives are grouped together in one set. When creating a constraint, you can specify multiple resources for the constraint to apply to.

resource template

To help create many resources with similar configurations, you can define a resource template. After being defined, it can be referenced in primitives or in certain types of constraints. If a template is referenced in a primitive, the primitive inherits all operations, instance attributes (parameters), meta attributes and utilization attributes defined in the template.

SBD (STONITH Block Device)

SBD provides a node fencing mechanism through the exchange of messages via shared block storage. Alternatively, it can be used in diskless mode. In either case, it needs a hardware or software watchdog on each node to ensure that misbehaving nodes are really stopped.

scheduler

The scheduler is implemented as pacemaker-schedulerd. When a cluster transition is needed, pacemaker-schedulerd calculates the expected next state of the cluster and determines what actions need to be scheduled to achieve the next state.

split brain

A scenario in which the cluster nodes are divided into two or more groups that do not know about each other (either through a software or hardware failure). STONITH prevents a split-brain scenario from badly affecting the entire cluster. Also known as a partitioned cluster scenario.

The term split brain is also used in DRBD but means that the nodes contain different data.

SPOF (single point of failure)

Any component of a cluster that, if it fails, triggers the failure of the entire cluster.

stickiness

Resource stickiness is a meta attribute that determines how much a resource prefers to stay on its current node.

STONITH

Another term for the fencing mechanism that shuts down a misbehaving node to prevent it from causing trouble in a cluster. In a Pacemaker cluster, node fencing is managed by the fencing subsystem pacemaker-fenced.

switchover

The planned moving of resources to other nodes in a cluster. See also failover.

utilization

Tells the CRM what capacity a certain resource requires from a node.

watchdog

SBD (STONITH Block Device) needs a watchdog on each node to ensure that misbehaving nodes are really stopped. SBD “feeds” the watchdog by regularly writing a service pulse to it. If SBD stops feeding the watchdog, the hardware enforces a system restart. This protects against failures of the SBD process itself, such as becoming stuck on an I/O error.