Database Reference
In-Depth Information
Implementing Availability feature
enhancements
Data recovery is a key step in providing availability to the systems. Hardware and software
play a vital role in helping the system to minimize the downtime. The more complex and
larger a database application, the more important it is to automate administrative tasks
with proactive maintenance tasks to ensure data is available. The key factors for hardware
and software solutions are cost, implementation, and feature support, which has its own
advantages and disadvantages.
Any high-availability solution must have provisions for hardware availability and data
availability. These two provisions must work in parallel to build an effective, high-availability
strategy, which requires planning and implementation at the SQL Server instance
configuration level. SQL Server 2008 R2 has no new features with regard to Availability;
with the only enhancements in this area being the performance improvements to database
mirroring, replication, and database backup strategies. This recipe covers the specific
availability performance improvements to Database Mirroring from SQL Server 2008 R2
version, which includes the configuration of endpoints, post configuration, and failover
process settings.
Database Mirroring (DBM) is the software solution for increasing the database availability,
where all the bulk operations are fully logged. The main benefits of database mirroring are:
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Increased data protection
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Increased database availability
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Automated failover support, which provides minimized downtime for the rolling
upgrade of databases
Before we begin with this recipe, it is essential to highlight the authentication options that
are required for the three SQL Server instances, which are referred to as partners: Principal,
Mirror, and Witness to communicate with one another.
The partner that owns Principal role stands as the main database. For hot standby provision,
the partner that owns Mirror role holds a copy of the database. The third partner in database
mirroring is called Witness that supports automatic failover by verifying whether or not
Principal server is functioning. It does not store any database information. By taking SQL
Server 2008 R2 new performance enhancements, it is ideal to set up database mirroring
pairs on a dedicated network adapter, as network configuration plays an important role in the
performance and transactional safety.
By default, the DBM endpoint requires the encryption of data that is sent over DBM
connections, which contains a bit of a performance lag. Unless you obtain a guarantee
that both the mirroring partners' network is secure, you should not disable the encryption
to gain performance.
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