CGTalk - Quantity Questions

xscript

11-07-2004, 01:53 AM

Hi!
First of all to say, I'm a newb in dual processor sistems and farms.

So, I'm buying a new comp and... Well, until now, I was thinking about single workstation: dual Opteron 2.2Gh and rest to match. Now, the part I don't like is that for a great deal of money, I get a comp that (if it's possible to calculate this way) works at about 4Gh. As the processing speed is my priority, that's not enough, especially in respect to the cost.
Now, I always hear stories about Render Farms, so... What if I have a Node, say 2.0Gh with 512 RAM, motherboard, LAN and case. If I take 10 of those, I still have enough for a Server: single low-end Xeon or even high-end P4, 2Gb RAM, hard etc. Now I have (not that I know anything about RenderFarms) 20Gh of processing speed.
Now, the question is: am I paying everything but performance when buying a high-end single comp, and is there more sense in buying a farm, even less ambitious? I mean, I intend to use this comp (or farm) for other things as well, not just rendering (not just 3D for that matter). I presume single comp makes a better choice then, but I'm not sure how much better?

I work in 3dsMax at the moment, but when I acquire this new comp, I'll be working in Maya (and Softimage).
I know that render farms are good for tasks which can be divided into independent chunks. And rendering is such task. What I would like to know is do all renderers work that way? I mean, there are dozen of renderers which support distributed rendering. Do all of them prefer a farm or there are some which prefer a single comp (dual processor perhaps)? And the ones which do prefer a farm; does the rendering time improves linearly with number and speed of Nodes (meaning if I have 10 Nodes with 2.0Gh, is it about 20Gh than)?

Another thing, I read on this forum many times that a farm is better for animations than is for stills; how much better? Does that apply for all renderers?

One last question - how do renderers work with RAM; is it OK for a Node to have way less RAM than Server?

Uh, many questions. : )
Thx in advance. I really appreaciate it.

P.S. Sory about my english...

Vertizor

11-07-2004, 05:34 AM

10 nodes each 2 GHz DOES NOT equal 20 GHz. Well arithmaticly yes, 2 x 10 = 20. But there are other bottlenecks to consider (network speed, etc.) A better measure is frames per hour. Even with a short 5 second animation you're still rendering roughly 30 fps (or what ever fps format you want to use). So how many frames per hour can one single computer render versus a farm of many computers? See where I'm getting with this? If it takes 1 hour to render one frame, if you had a farm of 10 computers then you'll finish 10 frames per hour.

With the exception of XSI, all other renderers to date splits the work by having each node render one frame at a time. So if you have 10 computers, you'll render 10 frames at a time (kind of like the example I gave above). That's why a farm is better for animations, more frames are rendered simultaneously. XSI Essentials and Advanced have the ability to split a single frame into regions and pass those to seperate nodes to render - so you may have more than one computer working on one single frame at a time which is good for still images.

DO NOT go cheap on RAM for the render nodes in your farm. If your scene needs 1 GB of RAM during rendering, then each node should have 1 GB of RAM. Also keep in mind that those 3 software packages you mentioned use Mental Ray. MR costs about $1000 for each additional node in your network render. Other high quality commerical renderers are pretty much the same story. So buying 10 cheap computers will end up costing you more.

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