UNIX for Advanced & Expert Users

We are trying to tune a server which phsycially is maxed out on cpu.
We are maxing out on memory and swapping at a rate of 20-43% of our swap space which is approx 45% of total ram.

We "can" upgrade to twice the memory that we currently have but it will be costly as there are no more seats left for memory, we would have to add a tray.

Given that we have maxed our cpu capacity, will it buy us much to add memory?

We are on digital alpha running digital unix. We have tuned our application to the best the business can live with.

Anyone have any experience to this depth of tuning?

If you're really short on both cpu and memory, you need a new box. If upping the memory is expensive don't that unless you're sure it will help.

It seems unlikely that you really are out of both resources simultaneously, but that it possible. And being out cpu may just indicate a poorly written program.

Before you spend a lot of memory on an upgrade, spend a little on an expert. Your local HP office should be able to provide an on-site expert for maybe $200 per hour. Or there may be other local rent-a-guru outfits. If nothing else, HP can fly one in, but you will pay for travel.

Ask for a 2 hour max appointment and schedule it during your busy period. He or she should have a pretty good idea of the usefullness of more memory at the end of that 2 hours.

Another approach...maybe your salesperson can lend you the memory for a couple of days.

Just out of curiousity....

What services are running on that server, how many users?
What are the specs for the server?

We run an ERP system. Even though we are global, the majority of our load is in North America, so our system loads are based the eastern time zone. Over night we run batch and backups and normally hit 100% usage on the cpu.. during the day when the batch processing is less but the users are on, we tend to start swapping but cpu is tolerable. We are on our way to a new box but not til next year.
Our server is outsourced, so it costs money to even investigate this. I am trying to determine if its worth the money to request getting a quote on adding the memory, knowing that its not just a matter of adding a memory card. Just hoping that maybe someone in the forum gets this deep into large installations.
:-) thanks

This is lot more info than you originally posted. Still, I would use a phrase like "dipping our toe in" rather than "this deep".

If you are sure that you are swapping and not just paging, then there is no question. You will benefit from more memory. But this only applies to daytime load where you see the swapping activity.

Your nightly jobs which are cpu bound will not benefit very much from the additional memory. Since these are batch jobs that are run overnight, why worry about them? Are they in danger of not completing overnight?

100% cpu could just mean you are compute bound. Imagine a system with one cput that is lightly loaded. Now I add a single process that is finding very large prime numbers. You now have 100% cpu utilization. This is not a real big deal all by itself. The process will have its priority lowered to the minimum very quickly. It will run only when no other process wants the cpu.

Now replace the cpu with a super cpu. My program will now find very large primes faster, but the cpu is still at 100%

So you may not have a problem with your nightly batch jobs. It's rare to use a computer for computation, but it does happen.

Also, next year is just a few months away. I would really resist investing in a system that is being replaced that soon.

Thanks for the response.
Yes, everything is relative. Its ok to max cpu if your system is running fine, that is good,but if the system is dogging, then maxing cpu means you don't have capacity for what you are running.

I think your response has given me some insight.....