[acasas]

Hi all,
I´m new on ansys, and I found that it requires big amounts of RAM and I/O processor speeds to produce reliable and fast reults on large models.
To make it simple, I´ll say that my processor will be an Intel Core I7 3820 at 3.6GHz and I´m willing to use 64 Gb Ram at 1600 Ghz., and willing to use Windows 7 pro 64 bits.
Ok, now comes my question:
For the best perfomance, should I install windows operating system and ansys program in a 2 diferent hard disk? should the working directory also be in another hard disk? should temporary directroy be in a another hard disk? and yet, when more than my 64 RAM memory its used, then should I use some more other hard disk for this purpose in a RAID 0 configuration? SSD (solid state disk) convinient? what SSD speeds recomended for my processor? what mother board should be used?
Thank´s a lot

[evcelica]

That's a lot of questions. I'll give my opinion on this but am not all that experienced with everything so you could do some research or wait for other contributors to answer as well. Are you using CFX, Fluent, Mechanical?

Which motherboard you use is up to you and what you need. From this question it sounds like you will be building your own computer? Just make sure you get a motherboard that will stably support 64GB of RAM, and make sure the RAM says its qualified with that motherboard or visa versa. I like the ASUS p9x79 deluxe, and P9x7-WS myself, though the ASUS boards don't support TRIM with SSDs yet, more on that later.

If you are going to be working on models that require more than the amount of RAM you have and you have to use your hard drive as RAM, (known as paging or disk thrashing) that is going to make a huge hit on your performance. Hard drives are orders of magnitude slower than RAM, and it would be almost pointless to have a fast CPU since you will be completely bottle necked by the hard drive. It would be better to either get a dual socket motherboard with 128GB+ of RAM or distribute across multiple 64GB computers.

With that said, if you have to disk thrash, a single SSD will be much faster than any HDD raid configuration. There was an ANSYS mechanical benchmark that showed an SSD 8x faster than a 15k RPM hard drive while solving out of core.

I don't believe you will get much speedup or difference from using a separate SSD for a working drive, but I do it anyways since then I can swap out or change that working drive anytime I want without affecting the operating system or other installed programs. I'm not sure whether ANSYS recommends you install the program on the boot drive or another drive though.

SSDs also benefit from "TRIM", but It doesn't seem possible to use TRIM on all motherboards when using them in RAID. TRIM is a command that erases unused blocks of data written in an SSD. If the SSD has to write to a block that has data in it already it has to erase that data before it can write, which affects performance obviously.

What I plan (not sure this is the right thing to do, but it sounds good to me with what I understand) is have one SSD as the boot drive with ANSYS installed on it. Then have two SSDs in RAID 0 as a working drive with nothing else installed on it. That way I can use "secure erase" as a manual trim until it is supported in RAID mode, which will hopefully be soon. One trim is supported in RAID mode, then maybe I would install ANSYS on the working drive as well.

Others input would be appreciated since I'm not 100% sure this would be the best configuration.