How bad is Virtual Memory vs RAM

[pwscottiv]

So I have 16GB of physical memory, but the analysis I need to run has
about 8 million quadratic hybrid tetrahedral elements, which is
requiring about 43 GB of space right now. The value peaked at about
70GB, when I think Abaqus was building the B matrix. I have two
dual-core 3.1GHz AMD Opteron processors
running on Windows XP Pro x64.However, now that I'm using virtual
memory, only one processor is pegged (25%), which is being used by a
program called "standard.exe" (part of Abaqus).

I submitted the
job, which is supposed to give me only basic stress and displacement
information, on 11/7/09 at 6:22AM (about 84 hours ago) and it has still
not finished. Earlier, I ran a analysis that had 2 million elements and
it took up about 18GB of memory and took about 2 hours to complete
using all 4 processors.

Right now, under the "processes" tab of
the task manager, standard.exe is only using 200k memory, and is maxing
out one CPU only. However, under the performance tab, it says that
68.2GB are being used. What's really odd, is that it appears Abaqus
isn't using any of my physical memory any more, only virtual memory. I
have nine 15,000rpm Seagate Cheetah hard drives that I split the page
files onto, hoping that would improve my performance. I wish I had the $4000 it would cost to upgrade to 64GB of RAM, but I don't...

So my question is, is this thing ever going to finish? This week, this month? Should I just give up?

Is there any way to tell how long it might take by knowing how many elements there are?

How much slower should this take using the type of hard <nobr style="font-weight: normal; font-size: 100%; color: darkgreen;" id="itxt_nobr_7_0">drives</nobr> I have instead of using physical memory?

Does it help or hinder me to split the page files onto different drives?

Is there anything else besides reducing the amount of elements that will make this work?

Thanks in advance for the help!

 

[Kaz Z06]

pwscottiv,

First off, I should mention that this forum is meant for discussion focused around the analysis tools found within the Pro/Engineer family of products. Mechanica would be the FEA package that would be of interest here, and is what you will find the most help with. Having said this, I can offer a couple comments - virtual memory is always much slower than physical RAM. Your OS and hardware will dictate just how much slower. Your problem sounds like you have far too many elements in your model given the hardware you have to run it on. Clearly the model needs to be simplified. My guess is with the RAM you have, you should limit your DOF to about 4-8 million, based on the type of model it is - single part, assembly with contact, dynamic, non-linear, etc.. You should try getting help on an Abaqus board as there may be some tricks you can use to maximize your resources through its tools.

Cheers,

Kaz