MySQL High Availability Technologies

Among various native and third-party solutions Edge Web Hosting supports two HA technologies for MySQL: native MySQL Replication and Continuent Tungsten clustering.

Native MySQL Replication

Edge suggests native MySQL replication for customers who:

  • Run MySQL on Windows or Linux
  • Needs HA Read-Only Caching
  • Linearly Scalable Read performance

The benefits of MySQL native replication include relatively easy setup and support, availability of monitoring, and low performance expenses. A read-only copy of your MySQL database is installed on each of your servers, which they read from directly. Any database writes are made to the master MySQL server, which is then replicated to your read-only MySQL servers. However, the native MySQL replication has its drawbacks. When implementing the load-balancing the application must be written to use separate connections for reading and writing the data. In the event of a write server failure, all nodes continue to have read local database availability, and writes are prevented until a new write master is promoted (normally a manual process). With informational websites that infrequently have database changes, these drawbacks are not substantial as the sites can rely on the high performance of the read-only databases and their isolation from central failures. With highly transactional systems (like an e-commerce application) this may not be an appropriate solution.

Continuent Tungsten Replication

Edge suggests native MySQL replication for customers who:

  • Run MySQL on Linux
  • Can use a JDBC enabled client
  • Need a Read/Write HA Solution (high number of transactions)

The Tungsten cluster takes over the built-in replication technologies of MySQL and adds an abstraction layer for automatic failover and read splitting among multiple nodes via a JDBC client. In this way it addresses the major drawback of the native replication making MySQL back-end truly highly-available. While failing over to a slave node Tungsten automatically redirects all of write client connections to the new master.

Summary

The following table summarizes the strengths and weaknesses of each approach.

Feature Native MySQL Replication Tungsten Replication
Available on Windows Yes No
Available on Linux Yes Yes
Real-time Replication Yes Yes
Automatic Failover No Yes
Load Balancing Read via Customer Application Read via JDBC Driver
Monitoring Yes Yes
Associated Cost Built-in Subscription, per Database Node
Minimum # of Servers 2 2

 

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