If I want to run a commodity hardware farm, say 100 eight-core machines, how much will this cost? I am also asking about incidentals like space to house the servers, T3 internet to the outside world, gigabit intranet, power, etc.
100 8-core servers, each 1U, figure $2K apiece as a rough guess. That is $200K.
Next you are talking about 3 racks of space (you can fit 42U in a rack), plus extra power, figure $3000 per month in a less-expensive colocation space.
Gigabit switches, cabling, etc. figure another 5K or more, depending on the quality and features you want.
Bandwidth will be metered by your colocation provider, prices can vary, usually you will be given 5-10Mbps as part of the rack.
You can physically fit 42U in a single rack, but you can't run that many servers off the regular per-circuit (which is often per-rack/cabinet) AC power limits most datacenters provide. Each circuit is usually 16-20 amps, this is in my experience about 8-10 2-3U servers (your hardware should have wattage and amperage documentation). You can get higher power density (and sometimes cheaper prices) if you use DC powered hardware. You can get more circuits, but they often charge incrementally more because as the servers per square foot ratio goes up, cooling requirements go up also (you pay for cooling as part of the price for the physical space), and the power limits are a way to help keep that under control, predictable, and homogenous across the datacenter.
Well, 100 1U servers is about 33 per rack if you have 3 racks; switches should not be more than 2U or 4U on top of that, and they do not use a lot of power.
Not sure exactly how much power, but 2x 30A power feeds will give 48A usable power, which is just about 1.5 amps per system. Whether that is enough for 8 cores (2x quad core), I don't know; will depend on amount of memory and disks.
Next you are talking about 3 racks of space (you can fit 42U in a rack), plus extra power, figure $3000 per month in a less-expensive colocation space.
Gigabit switches, cabling, etc. figure another 5K or more, depending on the quality and features you want.
Bandwidth will be metered by your colocation provider, prices can vary, usually you will be given 5-10Mbps as part of the rack.
So figure $210K plus $3K per month or so.