Availability Options

Note: Pivotal Platform is now part of VMware Tanzu. In v2.8 and later, MySQL for Pivotal Platform is named MySQL for VMware Tanzu.

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This topic describes and contrasts the topologies for MySQL for VMware Tanzu and explains the kind of availability each provides.

MySQL for VMware Tanzu Topologies

The topologies offered by MySQL for VMware Tanzu are:

Single node: This one-VM topology is inexpensive and good for testing. You can use this topology for apps where high availability is not important.
Leader-follower: This two-VM topology gives you redundancy through failover of the leader VM to the follower VM. For more information, see About Leader-Follower.
Highly available (HA) cluster: This three-VM plus jumpbox cluster uses a patched Galera cluster, Percona XtraDB Cluster (PXC), to provide the greatest availability of the topologies. For more information, see About Highly Available Clusters.
Multi‑Site Replication: This two-VM topology enables you to provision a leader and follower VM in two different foundations. For more information, see About Multi‑Site Replication.

The table below lists some key characteristics of the topologies to help you decide which one is best for your developers.

Topology	VMs needed	Pros	Cons
Single node	One	Simple Least expensive Straightforward operator experience Easy for the developer	No redundancy All data since last backup can be lost Data recovery requires restore from backup
Leader-follower	Two	Two copies of the data Data recovery is faster than single node	Less flexible tuning than single node Developers require some technical understanding Operator must initiate failover
Highly available cluster	Three and a jumpbox VM	Tightest RPO and RTO for downtime, including downtime for upgrades. See RPOs and RTOs below.	Most expensive Less flexible tuning than single node Developers require moderate technical understanding
Multi‑Site Replication	Two	Two copies of the data Data recovery is faster than single node Resilience to data center outages and upgrades Developers can initiate failover	Less flexible tuning than single node Developers require some technical understanding

Recovery point objective (RPO) and recovery time objective (RTO) are important considerations for availability.

The tables below describe the RPOs and RTOs for the topologies.

This table compares the recovery point objectives for the topologies.

Type of downtime	Single Node	Leader-Follower	Highly Available Cluster	Multi‑Site Replication
Planned Maintenance	Zero	Zero	Zero	Zero
Unplanned Downtime	Zero	Replica lag, or zero if in sync mode	Almost zero*	Replica lag
Data Recovery	Time since last backup	The time to initialize the follower VM, or zero if in sync mode	Almost zero*	Replica lag

*Database clients are notified that incomplete transactions are not saved.

This table compares the recovery time objectives for the topologies.

Type of downtime	Single Node	Leader-Follower	Highly Available Cluster	Multi‑Site Replication
Planned Maintenance	Time required to recreate the VM and reconnect to storage	Time required depends on the type of maintenance	Almost zero*	Time for developer to initiate switchover and for switchover to complete
Unplanned Downtime	Time required to recreate the VM and reconnect to storage	Time required to restore the VM or time for operator to initiate failover and for failover to complete	Almost zero*	Time for developer to initiate failover and for failover to complete
Data Recovery	Time to restore from backup	Time for operator to initiate failover and for failover to complete	Almost zero*	Time for developer to initiate failover and for failover to complete

*This includes time for apps to reconnect to the MySQL service instance.

When choosing a topology, risk is a factor to consider. Risk, in this case, encompasses the likelihood of:

Single node topology has the lowest risk. Highly available clusters have the highest risk.