Re: Projecting resource requirements

On Mon, 7 Mar 2005 14:00:19 -0800 (PST), David Turner <dnt9000_at_yahoo.com> wrote:
> Can anyone point me to some documents on calculating
> resource requirements for a project? I'm ok with disk
> consumption but cpu and memory seem harder to project.
>

I've worked with contractors who have horrendously complex spreadsheets they use to estimate resource requirments based on query types, date volumes and number of queries. They're usually wrong.

The following advice is based on several years working on IT projects in the public sector. Any pessimism or cynicism you detect is the result of several years working on IT projects in the public sector.

The best way to estimate is usually to find a system that is broadly similar, see what it's running on and how it's doing, add on a healthy contingency then scale up from there.

If it's a totally new system then the way I've found is best is to make an educated guess based on what I can find out, add 50%. Spec a system based on that estimate then see what the next model up is. Spec for the next model up fully loaded. Identify a system that has the power of the last system specced and the capacity to be expanded to twice that power. Get a quote on that.

So supposing you're inital guess plus 50% comes out to a Sunfire V240.  Next model up is a V440. A half loaded V880 is about the same as a fully loaded V440 so that's what you get the quote for.

If you're buying an app which the vendor has given you a spec for the hardware to run it on then at least triple that spec. Apps vendors will often under spec the kit they tell the project managers they'll need to buy to run the apps so as to make their product seem cheaper.

Stephen

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