topic Re: How to find how much "memory (RAM) and CPUs" need to be added in one server in Operating System - Linux

How to find how much "memory (RAM) and CPUs" need to be added in one server

senthil_kumar_1 — Mon, 25 Jan 2010 12:14:07 GMT

Hi All,

1)CPU utilization high:

We are having Suse 10 on HP Proliant BL465c - AMD. This has 2 dual core CPUs.

We are running some bigger jobs (related to 3D drawings) on that server.

So almost all the time CPUs are being utilized 100%.

We would like to increase the CPUs.

I have some questions:

1.1)How to find how much CPUs need to be upgraded to minimize the usage?

1.2)Is there any calculation to find this?

1.3)Is there any software to find this?

2)Memory utilization high:

One server is having 512 MB of RAM (on this server, 500MB of SWAP sapce have been utilized out of 2000MB) .

It is also being utilized fully most of the time.

We would like to increase the RAM.

2.1)How to find how much RAM need to be upgraded to minimize the usage?

3.2)Is there any calculation to find this?

3.3)Is there any software to find this?

Re: How to find how much "memory (RAM) and CPUs" need to be added in one server

Steven E. Protter — Mon, 25 Jan 2010 15:21:34 GMT

Shalom,

There is no real way to answer your question.

Right now demand for memory exceeds the supply.

You are asking us to predict future usage of memory on your system. If you upgrade the memory, the server will become more responsive, but people who have been avoiding it because its slow might start using it.

So:

How many users typically use this system.
How much memory does a single user of this 3D program need.

Multiply the two figures, that is your memory need.

You need to be realistic and project growth when calculating memory use.

SEP

Re: How to find how much "memory (RAM) and CPUs" need to be added in one server

Emil Velez — Tue, 26 Jan 2010 00:50:48 GMT

run top and look at the load average.

If your load average is 1.2 or .9 you are using 1 CPU all of the time.

If your load average is 4.0 that means that you have so many processes that are runable that you could possibly keep 4 cpus busy.

Think lines in the grocery store and checkout registers for a analogy.

You can look at the active virtual memory to see how much memory you might need plus how much swap space is actually used. If you use using swap space that means you exceeded your memory requirements by that much. Not reserved swap space actually used swap space.

Re: How to find how much "memory (RAM) and CPUs" need to be added in one server

senthil_kumar_1 — Tue, 26 Jan 2010 15:11:32 GMT

Hi Emil Velez,

I have found on my server.

load average: 4.32, 4.11, 4.03

Currently, I have 2 dual core CPUs, In linux it is showing as 4 CPU.

So if I am adding 1 more dual core CPU (2 CPUS), what will be the load average.

Can we find that using current load average?

Re: How to find how much "memory (RAM) and CPUs" need to be added in one server

senthil_kumar_1 — Wed, 27 Jan 2010 14:13:18 GMT

Hi All,

Could any of you do reply to my questions?

Re: How to find how much "memory (RAM) and CPUs" need to be added in one server

Steven E. Protter — Wed, 27 Jan 2010 17:26:43 GMT

Shalom,

top will show you current load average.

Your other questions:

load average: 4.32, 4.11, 4.03

Currently, I have 2 dual core CPUs, In linux it is showing as 4 CPU.

>> Load average is not a good way to measure how many CPU's you need. The way applications are written can skew these figures reather badly. All things being equal, adding two CPU's will probably reduce your load factor. But you might also find you need more memory.
<<

So if I am adding 1 more dual core CPU (2 CPUS), what will be the load average.

Can we find that using current load average?

SEP

Re: How to find how much "memory (RAM) and CPUs" need to be added in one server

MarkSeger — Sun, 18 Apr 2010 11:31:20 GMT

Sounds to me like steven's point in his first reply to you was the right one. If you reduce the load on your system and more users start using it, you'll be back to an overloaded system again.

Perhaps a different approach could help, if it's possible do even do.

What is the load on the system of one instance of this 3d application, assuming that is the problem? Maybe you can derive how many copies the system can support and limit the number of people running it? Can you get the system resource requirements from the application author/vendor and use that as a guideline?

-mark