Scaling on the cloud

Highly Available (HA) Architecture

Introduction

This reference architecture provides the best practices needed for planning, designing, and deploying High Availability (HA) architectures that can be followed for any Cloud Infrastructure Service. A high availability service or application is one designed for maximum potential uptime and accessibility. To design a high availability architecture, three key elements should be considered

1. Redundancy
2. Monitoring
3. Failover

Redundancy

Redundancy means that multiple components can perform the same task. The problem of a single point of failure is eliminated because redundant components can take over a task performed by a component that has failed.

Monitoring

Monitoring checks whether a component is working properly.

Failover

Failover is the process by which a secondary component becomes primary when a primary component fails. Although high availability can be achieved at many \ levels, including the application level and the cloud infrastructure level.

High Availability Building Blocks is by region is a localized geographic area composed of several availability domains. An availability domain is one or more data centers located within a region.

Availability zones/domains are isolated from each other, fault-tolerant, and very unlikely to fail simultaneously. Because availability domains do not share physical infrastructure, such as power or cooling, or the internal availability zone network, a failure that impacts one availability zone is unlikely to impact the availability of the others. All the availability zone/domains in a region are connected to each other by a low-latency, high bandwidth network.

This predictable, encrypted interconnection between availability domains provides the building blocks for both high availability and disaster recovery. Note that cloud Infrastructure resources are either specific to a region, such as a virtual cloud network, or specific to an availability domain, such as a Compute instance.

When you configure your cloud services, if the services are specific to an availability domain, it is important to leverage multiple availability domains to ensure high availability and to protect against resource failure.

For example, when you deploy a Compute instance, it resides in one particular availability domain. If there is no redundant deployment of this instance to another availability domain, the instance will be impacted when its availability domain encounters any issues.

Architecting High Availability Solutions

This describes each Cloud Infrastructure layer and provides detailed best practices and design guidelines for architecting high availability solutions.