Chapter 19. Options for high availability
Most organizations using SQL Server depend on it pretty heavily. It’s mission critical, as they say. The problem with mission critical is that computers and software break down from time to time. Hardware fails. A data file gets corrupted on disk. Or maybe you just need to maintain the server, applying a patch or two. What’s that? Mission critical means it has to be running 24/7, with no downtime for maintenance? That’s where high availability comes in.
This chapter is going to be mainly descriptive, meaning I’m going to explain how these technologies work and what they can do for you. We won’t be getting into their setup, because in some cases that can require a significant amount of server hardware. SQL Server Books Online provides step-by-step details for setting these up, if you need instructions.
High availability, or HA, involves building redundancy into your SQL Server platform. The idea is to have at least two of everything, so that if one fails, you’ve got a backup in place. SQL Server offers a number of different HA options, and you can implement HA practices that sit outside of SQL Server, too.