Joe D. wrote:

> Hello all; I have a question regarding replacing older Sun servers,
> particularly regarding CPU horsepower.
>
> Here's a for instance: We have a couple of 420R servers, with 4 GB Ram
> and 4 X 450MHz CPUs. In spec-ing replacements, I'm looking at V440
> servers. Since RAM is (relatively) cheap, I'm gonna spec the same
> amount of RAM, but CPUs are a different story. I can simply spec them
> with 4 CPUs, but on this model, the CPUs range from 1 GHz to 1.5 GHz.
> Plus, the price jump from 2 to 4 CPUs is about 10 grand (list, of
> course).
>
> Can I simply say "well, 4 X 450 GHz is 1800 GHz, so I'll spec them with
> 2 X 1.5 GHz CPUs for a total of 3 GHz of CPU power, and we'll be set
> for the current load, and have room for growth before we have to add
> processors"?
>
> I know, I know, I should have some stats gathered to gauge how well our
> 4 CPUs are doing for us now, but this was sprung on me last minute, and
> I need to get rough numbers to management ASAP.
>
> Any assistance, rules of thumb, or other advice gratefully
> acknowledged, as always.
>
> Joe D.
>

4 X CPUS does not compare well with N CPUS of different power. If there
are not N schedulable processes (or threads), you can't use all N CPUs.

I'd say your best bet is to tell management that they can have it done
right or they can have it Tuesday. If you don't have a good picture of
your workload and how your machines handle it, any recommendation you
make stands a good chance of being useless (or worse).

How much swapping are the current machines doing? If it's significant,
get more memory. Are you actually keeping 4 CPUs busy? If not, it's a
waste of money to configure four. If you are, you may want to think
more or faster or both.

Buying a new server is usually a substantial investment. Getting it
right is, therefore, usually worth the time and effort.