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Chapter 15. Multi-Site Clusters and Tickets

Table of Contents

15.1. Challenges for Multi-Site Clusters
15.2. Conceptual Overview
15.2.1. Ticket
15.2.2. Dead Man Dependency
15.2.3. Cluster Ticket Registry
15.2.4. Configuration Replication
15.3. Configuring Ticket Dependencies
15.4. Managing Multi-Site Clusters
15.4.1. Granting and Revoking Tickets Manually
15.4.2. Granting and Revoking Tickets via a Cluster Ticket Registry
15.4.3. General Management of Tickets
15.5. For more information
Apart from local clusters, Pacemaker also supports multi-site clusters. That means you can have multiple, geographically dispersed sites, each with a local cluster. Failover between these clusters can be coordinated manually by the administrator, or automatically by a higher-level entity called a Cluster Ticket Registry (CTR).

15.1. Challenges for Multi-Site Clusters

Typically, multi-site environments are too far apart to support synchronous communication and data replication between the sites. That leads to significant challenges:
  • How do we make sure that a cluster site is up and running?
  • How do we make sure that resources are only started once?
  • How do we make sure that quorum can be reached between the different sites and a split-brain scenario avoided?
  • How do we manage failover between sites?
  • How do we deal with high latency in case of resources that need to be stopped?
In the following sections, learn how to meet these challenges.