SQL Server is used by business applications, web applications, individual programmers, and for content-intensive websites. Microsoft SQL is popular among the developers because it is a powerful, expandable, and upgradeable choice for database solutions. Microsoft SQL Server 2012 is equipped with various features. Many server makers have built products based on this platform, such as the Dell SQL server. We will be discussing the AlwaysOn feature of SQL Server 2012 in this article.
For the sake of explanation, you can consider AlwaysOn as a secondary server, which is reserved for failover environment. The secondary server remains active and works continuously. Its response time is somewhat slow, but the applications do not suffer any data loss.
Before the new version of the MS SQL Server, two methods were typically used in order to achieve high availability. The first method was to replicate the primary server to the secondary server through log shipping. The second method was the creation of a standby server through clustering, which upon failover could take the role of the primary server. Both of these methods had their own flaws. The first method is time consuming because of the unavailability or inaccessibility of the database, and the second method is quite expensive, as we need numerous servers remaining idle unless a failover environment occurs.
The AlwaysOn feature is basically inspired by Exchange Server 2010. Though there is one drawback of the AlwaysOn feature, bandwidth hungry, the inspiring feature of AlwaysOn makes it quite popular. The applications using multiple databases can use AlwaysOn Availability Group to guarantee high availability. When the primary site shuts down due to heavy failure, the Availability Groups can be extremely helpful for migrating database accesses from a primary to a remote site. More than one Availability Group can be used for a single SQL Server 2012 instance.
Benefits Of AlwaysOn Availability Groups
It supports encryption and compression, therefore, securely and quickly moving the data across the network.
Each AlwaysOn Availability Group can support one primary replica and a maximum of four secondary replicas. In this way, each Availability Group can support a maximum of five replicas.
It supports multiple availability group failover. This includes automatic failover, planned manual failover, and forced manual failover.
It supports automatic corrupted page recovery. The page may be corrupted as a result of the errors. Once the page is corrupted, the AlwaysOn availability group requests the page from the primary or secondary replicas and replaces the page with the latest fresh copy of the page. In this way, the page is recovered.
Setting up and managing Availability Groups is easier with the tools provided.
High availability is an important requirement of many applications of enterprise-level. Before the existence of AlwaysOn, high availability was achieved mainly through clustering, but now with AlwaysOn, there is an official support for this technique. Without doubt, the AlwaysOn feature makes our system powerful, flexible and scalable, ultimately bringing a safer network environment.