[Beowulf] cluster advice

[asa hammond]

Hello all. I am going to be building a cluster to handle image  
rendering and processing and I wanted to get some advice.  The  
cluster will have 2 kinds of problems to crunch on,
1) heavy cpu style jobs with moderate IO and
2) heavy IO jobs with up to 200 meg image retrieval off of the file  
server and moderate cpu requirements.

We have 10-14k to spend on the nodes at the moment.

What are your thoughts on the best node configurations to purchase.
If we go with dual core athlon64 x2's  we can get about 10-12 nodes  
with single cpu motherboards.
Any reason to go with dual opterons over the dual core athlon64s if  
the cache sizes and clock speeds are the same?

Any alternative case systems you all have experience with?  Do any of  
you run without cases a la early google? Everything at the moment is  
rackmount cases but we figure if we are using micro atx boards we  
could fit two boards per 1U front to back with good cooling on  
aluminium rackmount trays.  Anyone doing such extreme cost-cutting  
measures to save on the obscene rackmount case+rail costs?

Any mobo recommendations?  What is your feeling about the micro atx  
boards?  not longterm reliable?  We don't need any of the fancy  
extras most gamer and server motherboards have. All we need to have  
is pxe bootable gigabit(dual on mobo would be great), slots for ram  
(2 gig) and a cpu.  We can go with a gigabit on the board and add an  
extra nic to get two total, etc.

We are interested in going the channel bonding route for better than  
gigabit throughput with 2 ports per node, each feeding into a  
separate switch connected to separate ports on the server.

Any switch recommendations?  Do I need to go with a layer 3 switch if  
all I am doing is running my machines this way?  We are thinking  
several 16 port netgears. We want to go for future-proof  
expandability as we will be adding nodes as we can afford them.

Heating is becoming an issue as well.  We have  an 8x10x6 foot room  
with no AC. Just forced air cooling.  Any good cooling advice for  
remote AC as well as any kind of quiet passive cooling would be very  
useful.  We need about 1.5 ton of cooling as far as I can figure.   
Ambient air temp is 73 deg and room is running at 84-89.

Pointers to any info would be great.  This has all been discussed  
before but now those recommendations are a bit outdated as the march  
of moore goes on.

Thank you all in advance.  This list has tons of great information.   
A great resource for all of us.

Asa