Database Reference
In-Depth Information
Log Shipping allows the maintenance of a copy of the database on multiple secondary servers by applying
a continuous stream of log backups. It does not protect against data loss for the period since the last backup
was applied.
Replication allows you to replicate a subset of the data from the database across multiple databases allowing
read/write access in each location. Transaction replication has low latency for the changes to be distributed across
subscribers. However, setting up and monitoring a complex replication topology is a very challenging task.
Designing a high availability strategy is an iterative and interactive process that requires you to work with other
members of the technical team as well as with stakeholders. You must make sure that RTO and RPO requirements are
realistic and achievable within the budget allocated to the project.
The choice of high availability technology depends on the requirements and budget as well as on the version and
edition of SQL Server installed. You are not restricted to a single technology—it is often beneficial to combine a few
technologies together.
You should consider the performance implications of the technologies that uses synchronous commit, especially
if the system has a performance SLA which dictates latency for some OLTP transactions.
It is extremely important to test your high availability technology and perform failover after it is implemented
in production. It is better to find and fix any issues in a controlled environment rather than to fight with them after a
disaster occurs.
You should regularly re-evaluate the high availability solution you implement based on database size and activity
growth, especially if your secondary stand-by servers are less powerful than your primary ones.
