Summary

Database mirroring provides a database redundancy solution using the log-transfer mechanism. The log records are sent to mirror log as soon as log buffer is written to the disk on the principal. Mirroring can be configured in either high-performance mode or high-safety mode. In high-safety mode, if the principal fails, the mirror server will automatically become a new principal and recover its database. Understanding the application behavior in terms of log-generation rate, number of concurrent connections, and size of transactions is important in achieving the best performance. The network plays a very important role in a database mirroring environment. When used with a high-bandwidth and low-latency network, database mirroring can provide a reliable, high-availability solution against planned and unplanned downtime. In Chapter 18, we look at the backup and recovery options SQL server provides in detail.