Downtime for any application can have a negative impact on a business, resulting in lost revenue, reduced customer satisfaction, and damage to the business's credibility. Many database applications, especially enterprise business applications, require system downtime to be kept to a minimum. System downtime occurs for a variety of reasons, such as human error, natural disasters, hardware or software failures, and application upgrades. Obtaining high availability is a common requirement for many businesses. Whether a solution is suitable for a specific application scenario depends on many factors, and the solution that performs best in one situation may not necessarily be the best in another. For example, the following application scenarios:
◆An Internet-based sporting goods retailer wants to provide its customers with near-continuous availability. A Web server has been added to the Web farm, but a database failure can produce errors. Most of the time, these situations cause the company to lose customers. The company already had an approved version of the standard server and hoped to avoid spending a lot of money, changing infrastructure or rewriting applications.
◆Headhunting companies are very concerned about the errors their users encounter when using customer databases. Although immediate failover was not necessary, the company still wanted to have a warm standby server that could be quickly brought online.
◆The insurance company wants to provide near-continuous availability for its claims database. The performance of the system must not be compromised, and documents currently stored in the file system to support the claim must be available.
◆The management training company has three sites, each site has a sales team. The sales team enters records from their respective sites into the Orders database. To improve performance, each site is required to be able to access all of the company's orders on a local server. To provide availability when a failure occurs, each site must be able to switch to a server at the other site.
◆Accounting firms want to provide availability to their clients even in times of failure, such as natural disasters. Information doesn't have to be available immediately, but it should be available within hours, not days. The company also wanted to save the information in the database on a daily basis to meet regulatory requirements. The copied data does not need to be available immediately, but it must be available for many years.
◆A toy manufacturer wants to compile a report based on a sales database, but because the database is always in use, the report preparation process is often interrupted by transactions currently being executed. The company wanted to be able to compile reports on unfiled transactions, but this would produce incorrect results because some transactions were incomplete.
◆The real estate company wants to protect the system when users make mistakes and wants to be able to restore the recorded values from the previous day. The company also wanted to be able to compile reports based on the previous day's data because they would not be affected by the same day's trading. Ideally, the company would like to implement a solution with minimal disk overhead.
Based on various availability requirements, enterprises need a database platform that provides flexible options for high-availability solutions. In this white paper, you can see how SQL Server 2008 Always On technology provides flexible options for high availability, allowing enterprises to implement the best solution for their specific needs.
-