Chapter 15 High Availability and Scalability

Table of Contents

15.1 Using MySQL within an Amazon EC2 Instance
15.1.1 Setting Up MySQL on an EC2 AMI
15.1.2 EC2 Instance Limitations
15.1.3 Deploying a MySQL Database Using EC2
15.2 Using ZFS Replication
15.2.1 Using ZFS for File System Replication
15.2.2 Configuring MySQL for ZFS Replication
15.2.3 Handling MySQL Recovery with ZFS
15.3 Using MySQL with memcached
15.3.1 Installing memcached
15.3.2 Using memcached
15.3.3 Developing a memcached Application
15.3.4 Getting memcached Statistics
15.3.5 memcached FAQ

Data is the currency of today's web, mobile, social, enterprise and cloud applications. Ensuring data is always available is a top priority for any organization. Minutes of downtime can result in significant loss of revenue and reputation.

There is no one size fits all approach to delivering High Availability (HA). Unique application attributes, business requirements, operational capabilities and legacy infrastructure can all influence HA technology selection. And technology is only one element in delivering HA: people and processes are just as critical as the technology itself.

MySQL is deployed into many applications demanding availability and scalability. Availability refers to the ability to cope with, and if necessary recover from, failures on the host, including failures of MySQL, the operating system, or the hardware and maintenance activity that may otherwise cause downtime. Scalability refers to the ability to spread both the database and the load of your application queries across multiple MySQL servers.

Because each application has different operational and availability requirements, MySQL offers a range of certified and supported solutions, delivering the appropriate levels of High Availability (HA) and scalability to meet service level requirements. Such solutions extend from replication, through virtualization and geographically redundant, multi-data center solutions delivering 99.999% uptime.

Selecting the right high availability solution for an application largely depends on:

The primary solutions supported by MySQL include:

Further options are available using third-party solutions.

Each architecture used to achieve highly available database services is differentiated by the levels of uptime it offers. These architectures can be grouped into three main categories:

As illustrated in the following figure, each of these architectures offers progressively higher levels of uptime, which must be balanced against potentially greater levels of cost and complexity that each can incur. Simply deploying a high availability architecture is not a guarantee of actually delivering HA. In fact, a poorly implemented and maintained shared-nothing cluster could easily deliver lower levels of availability than a simple data replication solution.

Figure 15.1 Tradeoffs: Cost and Complexity versus Availability

As the number of “nines” in the uptime percentage increases, so does the cost and complexity, progressing from basic replication, to a clustered and virtualized configuration, to shared-nothing clusters replicated across geographic regions. Different kinds of organizations require different “nines” of availability, from Internet service providers and mainstream businesses at 3 nines, online services at 4 nines, and eCommerce, telecom, and military applications at 5 nines.

The following table compares the HA and Scalability capabilities of the various MySQL solutions:

Table 15.1 Feature Comparison of MySQL HA Solutions

RequirementMySQL ReplicationMySQL Cluster
Platform SupportAll Supported by MySQL Server ( Supported by MySQL Cluster (
Automated IP FailoverNoDepends on Connector and Configuration
Automated Database FailoverNoYes
Automatic Data ResynchronizationNoYes
Typical Failover TimeUser / Script Dependent1 Second and Less
Synchronous ReplicationNo, Asynchronous and SemisynchronousYes
Shared StorageNo, DistributedNo, Distributed
Geographic redundancy supportYesYes, via MySQL Replication
Update Schema On-LineNoYes
Number of NodesOne Master, Multiple Slaves255
Built-in Load BalancingReads, via MySQL ReplicationYes, Reads and Writes
Supports Read-Intensive WorkloadsYesYes
Supports Write-Intensive WorkloadsYes, via Application-Level ShardingYes, via Auto-Sharding
Scale On-Line (add nodes, repartition, etc.)NoYes