Sql Server Mirroring


SQL Server 2005 provides a set of high availability methods that the users can use to achieve fault tolerance and to prevent server outages and data loss. The selection of the high availability method depends on various factors. Some DBAs need the servers to be available 24/7, while others can afford an outage of a couple of hours. Cost also plays a role in the selection. For example, Clustering is an expensive high availability method when compared to Database Mirroring, but it allows the user to failover immediately.
The following high availability features are available with the Enterprise edition:
Failover ClusteringMultiple Instances(up to 50)Log shippingDatabase SnapshotsDatabase MirroringThe following high availability features are available with Standard Edition:
Failover Clustering(maximum two nodes)Multiple instances(up to 16)Log shippingDatabase MirroringIn this article, we will be discussing about Database Mirroring high availability method.
Overview of Database Mirroring
Database Mirroring is a primarily software solution for increasing database availability. Mirroring is implemented on a per-database basis. Mirroring works only with full recovery model. Database mirroring is available in the Enterprise edition and in the Standard edition. The user can mirror only the user databases.
Mirroring allows the user to create an exact copy of a database on a different server. The mirrored database must reside on different instance of SQL Server Database engine. Microsoft fully supports database mirroring with SQL Server 2005 SP1 onwards. For the RTM release (prior to SP1), Microsoft support services will not support databases or applications that use database mirroring. The database mirroring feature should not be used in production environments. Prior to SP1, database mirroring is disabled by default, but can be enabled for evaluation purposes by using trace flag 1400.  The following T-SQL statement can be used to achieve this:
Benefits of Database Mirroring:
1.Implementing database mirroring is relatively easy.It does not require any additional hardware in terms of clustering support.So it proves to be a cheaper implemetation instead of cluserting a database.
2. Database mirroring provides complete or nearly complete redundancy of the data, depending on the operating modes.
3.It increases the availability of the database.

Ref: http://www.sql-server-performance.com/articles/clustering/mirroring_2005_p1.aspx

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abhilash, is a programmer by profession and a technology addict with a passion towards browsing , shopping and imaging . My views may be biased on reviews. all images and videos are copyrighted to respective owners.


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