"Are you running your database in a virtual machine?" is one of the first questions to ask when someone is experiencing very bad performance from their database server.

It's right up there with, "Does your database need reorganization?", "Is your hard drive fragmented?", "Are you running with OPTIMIZATION_GOAL = 'First-row'?" and "Have you waved a dead chicken over the keyboard yet?"

From what I've been told (I am not a VM expert) it is very easy to screw up the VM setup so the performance of even a lightly loaded database sucks (I could point to one that's visible on the web, but I'm under NDA).

In other words, VMs make system administrators more important, not less. If your system administrator is like my system administrator, stay away from VMs... just kidding... no, that's true... wait, I was joking... [thwack] [ouch]

Here's the truth: There ain't no such thing as a free lunch.

We also have clients running SA11 in a virtual environment (DB size 6 to 10 GB). If enough memory is assigned to the VM, everything runs smoothly.

BTW virtualization helps them to ensure that not all resources are devoured by other services (SQL Server, Exchange Server to name a few) without having to dig deep into specific configuration details.

We have a few clients that do this, and it works extremely well for them.