Calculating the cost of a computing cluster?

Question

Data center

Interested in the issue of scalability and technical organization of cluster computing.
Namely, how does the cost of creating a cluster change depending on the number of computers in it?
For example, I can build a small cluster for 3-5 computers at home and its cost will be equal to the price of computers.
If you increase the number of computers, then you will not be able to assemble such a cluster at home, you will need to rent a room with sufficient power supply, racks, cooling systems, fire extinguishing systems, and more complex network equipment. It is clear that with an increase in the number of computers in a cluster, the cost of additional equipment increases, but it is rather difficult to calculate by how much.
The following questions arise：
1. How much will additional equipment cost and what are the requirements for rooms to host clusters of 25/50/100 computers?
2. What is the maximum number of computers that can be placed by equipping a server room in an office building?
3. Starting from how many computers does it make sense to build a separate data center?
I will be very grateful for the answers and for the links on the topic!

Answer 1

At 25/50/100, if the cost of renting a room is expensive, then you need to look towards blade solutions.
For example, when using the IBM E series ( www-03.ibm.com/systems/ru/bladecenter/hardware/chassis/ )
A standard rack (42 units) will include 6 chassis, 14 "blades" in each, and that 84 "servers ".
If, on the contrary, the rent is cheap, then you need to look towards a self-assembly option, like the one from Google.

Answer 2

1) Depending on what you will switch these servers on, if we say on a gigabit ethernet without problems, then this will affect the cost of iron by no more than 10 percent.
2) It depends on what kind of electrical ceiling the wiring to this room can withstand, the size of the room and how many conduits you can put into this room.
3) FROM three racks, you should think about a small data center, it will most likely be more profitable than renting, but not a fact.