Availability Options

Note: In v2.9 and later, MySQL for VMware Tanzu is named VMware Tanzu SQL with MySQL for VMs.

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

VMware Tanzu SQL with MySQL for VMs Topologies

The topologies offered by Tanzu SQL for VMs 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.

Pros and Cons

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

TopologyVMs neededProsCons
Single nodeOne
  • 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-followerTwo
  • 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 clusterThree 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 ReplicationTwo
  • 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

RPOs and RTOs

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.

RPOs

This table compares the recovery point objectives for the topologies.

Type of downtime Single Node Leader-Follower Highly Available Cluster Multi‑Site Replication
Planned MaintenanceZero ZeroZeroZero
Unplanned DowntimeZero Replica lag, or zero if in sync modeAlmost zero*Replica lag
Data RecoveryTime since last backup The time to initialize the follower VM, or zero if in sync modeAlmost zero*Replica lag

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

RTOs

This table compares the recovery time objectives for the topologies.

Type of downtime Single Node Leader-Follower Highly Available Cluster Multi‑Site Replication
Planned MaintenanceTime 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 DowntimeTime 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 RecoveryTime to restore from backup Time for operator to initiate failover and for failover to completeAlmost zero* Time for developer to initiate failover and for failover to complete

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

Risk

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

  • Operators being interrupted to perform disaster recovery

  • Encountering issues because of the complexity of the topology and technology

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

TopologyRisk-level
Single nodeLow
Leader-followerMedium
Highly available clusterHigh
Multi‑Site ReplicationMedium-high