Q:

If you were asked if a system could sustain double growth, what 3 things would you do to answer?

Let's say at your job your boss says,

That system over there, which has lost all institutional knowledge but seems to run pretty good right now, could we dump double the data in it and survive?

You're completely unfamiliar with the system.
It's in SQL Server 2000 (primarily a database app).
There's no test environment.
You might be able to hijack it on the weekends if you needed to run a benchmark.
What would be the 3 things you'd do to convince yourself and then your manager that you could take on that extra load. And if you couldn't do it, on the same hardware... the extra hardware (measured in dollars) it would take to satisfy that request.
To address the response from doofledorfer, you assumptions are almost all 180 degrees off. But that's my fault for an ambiguous question.

One of the main servers runs 7x24 at 70% base and spikes from there and no one knows what it is doing.
This isn't an issue of buy-in or whining... Our company may not have much of a choice in the matter.
Because this is being externally mandated, delays in implementation could result in huge fines. So large meeting to assess risk are almost impossible. There is one risk, that dumping double the data would take the system down for the existing customers.

I was hoping someone would say something like, see if you take the system off line Sunday night at midnight and run SQLIO tests to see how close the storage subsystem is to saturation. Things like that.

A:

Set up a test environment, even if I have to do it on my laptop.
Enable some kind of logging on the production system to get an idea of the volume of transactions in addition to the volume of data.
Read the source code as I run stress tests on my laptop with increasing amounts of data.

Having said that, I sympathize with this assignment, because it's unfair.  It's like asking someone in a boat if the boat can float with twice the cargo -- but you can't get out of the boat or take it out of its regular service.

