It's really an interesting idea to keep mining rig cool during the summer
But here is some of my concern, I might be wrong in doing my calculation coz I've never dealt with datacenter space rent.
From data you provide,
1U rackspace comes with 90W of power costs $20/Month, I only consider in terms of power supply (not space in the rack) ATM,
in order to power a 4-video cards ming rig, it requires 7-9 blocks of 90W depends on cards, so that is $20 for the first 90w block plus another 6-8 90W blocks @ $15/each, that's about $90-$120
So only power supply will cost around $100/month/rig
I've read through a little on the forums here and saw one GPU can use around 200-250W of power.
The all-inclusive (conditioned power with UPS, BW, rackspace) cost in the model I proposed is around $0.30/kWh ($0.30 * 0.09kW * 744h on a month = $20.09).
Comparison: Domestic/Residential power in the US is around $0.10-0.17/kWh (source:
http://www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_5_06_b), but don't forget air conditioning expenses (without being optimized as in a datacenter you are looking at least at a PUE of 2, so $0.20-0.34/kWh) and bandwidth (mining uses almost nothing but still you have a minimum monthly internet bill to pay at home). Not even counting the initial investment on a UPS and on an airconditioning unit.
Now, get back to space in the rack, a full size video card is about 5 inch and a typical 2U is about 3.5 inch, I don't know if there is enough space inside to accommodate a typical 4-video cards mining rig.
For ppl who are using FPGA might be a good idea?
Usually on rackmount servers a video card will be sideways 90 degrees from the motherboard (facing the floor/top) connected to the motherboard by a riser card. On a 1U you can fit up to 2 PCI slots on a single case depending on the case.
On a 2U you usually can fit 4 or 5x half-height, full length cards.
Supermicro also has servers that go up to 4x GPU PCI-e slots distributed over the chassis in 1U or 2U config.