Dear fluent users,

we're about to order new hardware for our fluent simulations. I've followed the discussions about hardware in this forum and decided to go for a dual Xeon 2 GHz with 2 GB of PC800 RDRAM from Dell. We want to run Fluent under Linux, but in Europe Dell sells its machines with Windows only. Now comes the point which puzzles me: in the US you can order machines with Linux preinstalled from Dell. If you choose Linux as OS you can order only Xeon CPUs up to 1.7 GHz. If you choose Windows XP or 2000 you're allowed to choose Xeons with 2 GHz. So far I didn't get any information from Dell, what's the reason for this. Neither could I find any information, if you can install a recent release of Suse or Redhat on a system with the i860 chipset and two Xeons with 2GHz without running into problems. Anybody out there who is using such a machine under Linux or understands the sales strategy of Dell?

thanks for helping, Christian

I don't know about the 2GHz, I can however give you some advice concerning the Precision 530 - we have evaluated a dual CPU 1.7GHz 530 for a few months. It runs Fluent very well. RedHat 7.1 installed without any problems (we also could not order it with Linux factory installed). We haven't tried 7.2 yet but will do soon. You have to get an unofficial Fluent release from your support office though to run on RedHat 7.1 - the last official release doesn't work on 7.1, but they have a fixed version which I'm sure they will give you if you ask.

About graphics - we tested both the Quadro and the Fire-GL cards and I'd definitely recommend the Quadro. The Quadro is more robust once you install the latest drivers from nvidia.

Thank you Jonas! Installing Linux on a dual Xeon 2GHz doesn't give any problems, as I found another company selling exactly this configuration with Linux preinstalled. Maybe it's just MS-friendly marketing of Dell...?!

A fiend of me still had problems with last release of fluent (for the newest glibc). I'd prefer to wait for fluent6.

Why xeons ?

Fluent has an unofficial 5.7 version which runs very well on RedHat 7.1.

Xeons because you can get a dual-CPU motherboard with 4GB RDRAM with them.

Jonas:

Could you comment on Linux vs W2k I am running Fluent on W2k without any problems. What would be the advantages of switching to Linux? speed? stability? Linux vs W2k price? easy to use, user friendly? ???

Thanks Peter

According to our experience running Fluent on Linux is faster than on Win2000 for both one and two processor case (for two processors is the speedup even bigger).Does anybody have different experience ?

I have very limited experience from Fluent on W2K (I have tried it once). In any case I don't think that there is a big difference, the windows version of fluent used to be more buggy but I have heard that they have sorted out most problems by now. The speed is similar - about a year ago the windows version was slightly faster on single CPU and scaled slightly worse on multiple CPUs. This was on PIII, I don't know if this is still true for the P4.

The main advantage with linux is that it integrates very well with a larger compute environment. We have a linux-cluster with 150 CPUs and we have many UNIX workstations. With linux we can easily log into and use whichever computer we want. Running W2k in this environment would be much less convenient.

In a single user single-machine environment W2K is probably an equally good choice though - chose the OS that you prefer to work with yourself.

It was fluent5.7 (the unofficial version) and it did not work on suse7.1 or 7.2 (sorry, don't know exact..)

Dualboard ? ok. Did you also test a network-cluster with the "normal" P4-cpu.? Isn't it much cheaper than a dual-board, and in a year or two, you can also upgrade the single-pc with a faster "normal" cpu or put the the hardware on your table for word and excel and buy a new small cluster ?

I don't think this is vendor specifid, but I have experienced some problems with Fluent and W2K. I was trying to run 8 different machines and almost every attempt (say 9/10) a random machine out of the 8 would not connect.

I'm not positive this is the ultimate reason but based on limited research at msn.com it seemed to me a max of 10 connections are permitted at one time by any machine if you only have W2K workstation and not W2K server. I don't know how much more money you have to give Bill Gates to get Server over the Workstation version. So you're limited to a max of 10 CPUs theoretically in parallel, assuming no machine is talking to anything else on the network but the other CFD slaves, but practically even getting 8 CPUs going at once was a little painful.

Didn't really compare speed up to serial because the case was too big for any one machine's memory. At least once it was going, (ie 1/10 times) I could launch all kinds of jobs without shutting down Fluent. If this same problem applies to CFX, launching parallel will be even less reliable since it has to reconnect to every machine for every job. But I haven't pushed CFX to more than 4 processors yet so I can't say it's had a fair trial yet.

Overall I think this is just another reason to run Linux over W2K for CFD.