If you’re a full time production database administrator, you need a staging environment.
This is where you test infrastructure tasks like failing over mirroring, doing a disaster recovery role swap, cluster quorum changes, log shipping configuration, and patching. You need to test this stuff repeatedly so that when you’re under pressure in the production environment, you feel comfortable and confident. Bonus points if you use this environment to build checklists and screenshots for rarely-done tasks like recovering from corruption.
You can’t use the development or QA environment because many of these tasks will take the entire environment down – sometimes by design, and sometimes by accident. If you’re in the middle of testing a patch at 9:30AM, and something breaks, and you’ve got a meeting starting at 10AM, you don’t want to have the entire developer team sitting idle because their SQL Server is down. You want to be able to leave this environment in a broken state for hours or days without feeling clock pressure.
Staging is the DBA’s development environment.
You’re not going to use it for load testing or performance tuning, just rehearsing and testing infrastructure changes you might make in production. As such, the hardware quality and quantity doesn’t have to matter, but it needs to be as logically similar as possible.
For example, if your production environment consists of a 3-node production failover cluster and a 2-node cluster in DR, with log shipping across the two, then you’re going to want at least one cluster, plus a separate server to log ship to.
The individual nodes can be low-powered boxes – think single-CPU desktops with 16GB RAM and a couple of $250 1TB SSDs. (You want SSDs because you’re going to be doing a lot of backup/restore on these.) In theory, they can be VMs too, but often sysadmins freak out when you start asking for several terabytes of shared storage space for a staging environment. For $250, I can just avoid that argument altogether.
Use SQL Server Developer Edition – it’s free – and this whole thing costs you less than a grand.