During normal companion mode, performance of system procedures that update user information (sp_addlogin, sp_addrole, and so on) and of commands such as create database is slightly degraded because the primary companion must perform the command locally, then synchronize with the secondary companion. For example, if you add user “joe” to the primary companion, both the primary companion and the secondary companion must update syslogins to include this new user.
Performance after fail over depends on the configuration of the secondary companion. If the secondary server is configured similarly to the primary server, performance should be similar before and after fail over. However, if the secondary server is not as robust (for example, has less memory or fewer CPUs) as the primary server, then performance after fail over is degraded. The performance of the secondary companion can also be degraded after fail over because it is running the primary companion as well as any applications.
