Introduction

Business continuity is of utmost importance in today's world. An application downtime that's even as low as a few minutes may result in potential revenue loss for companies such as Amazon and Flipkart. Downtime not only results in direct revenue loss as transactions are dropped as and when downtime happens, it also contributes to a bad user experience.

Often, application downtime because of programming or functional issues doesn't affect the entire application and can be fixed by the developers quickly. However, downtime caused by infrastructure or system failure affects the entire application and can't be controlled functionally (by the developers).

This is where high availability (HA) and disaster recovery (DR) are required. In this lesson, you'll learn about high availability and disaster recovery concepts and terminology, and the different solutions that are available in Microsoft SQL Server to achieve HA and DR.

The type of HA and DR solution implemented by a business depends majorly on the service level agreement (SLA). The SLA defines the recovery point objective (RPO) and recovery time objective (RTO), which will be discussed in detail later in this lesson.