How many servers does a data center have?
There is no perfect way to gauge how many servers are in a typical data center, but there are a few ways to go about estimating it. If you judge by how many servers can fit in a 8-tile pitch configuration within a certain amount of square feet, there could be up to 2,688,636 1U servers in a high tier data center.
A more accurate estimate might come from calculating how many servers could be used with a given energy capacity. If a similar high tier data center has an 850 mW capacity, and each rack was using 25 kW of power, that institution could operate 1,768,000 1U servers.
Data centers tend to withhold many details of their operations for security purposes. Still, with our experience assisting data centers, we can navigate through the steps needed to estimate how many servers a typical data center might have.
How large are server rooms inside data centers?
We can only guess how large the average server room is inside of a data center because companies typically don’t disclose this information. For purposes of estimating how much servers are in a reputable data center, we will assume that data centers are trying to maximize server room space.
Of course, a data center needs offices for executives, system administrators and security. They also need a cafeteria and/or leisure spaces for their employees. Data centers typically exist on the outskirts of populated areas, so they might compensate for traveling distance with nice amenities.
There is also space-hogging infrastructure that is necessary to maintain a functioning cluster of servers. This infrastructure mostly consists of HVAC systems and power distribution hardware.
So, for the purposes of estimating an average, we will assume that 65 percent of the total square footage of a data center consists of the floor tiles that make up a server room.
The answer is in the floor tiles
Analyzing data center space whether to speculate or build can look intimidating, but the standardization of floor tiles makes the process very simple.
The standard Data Center Rack has a 4 ft depth and 2 ft width which means it occupies 1 floor tile in width and 2 in depth. This isn’t always the case.
Many server racks have a 3 ft depth and 2 ft width which is what popularized the “7-tile pitch” (seen in the photo above) a reality. The 4×2 data center racks will need 8 tiles in width in order to have adequate walking space in the cold and hot aisles of the ‘pitch.’
This is all to say that depending on what size racks a data center is using, they will occupy different amounts of floor space. For the sake of making comfortable estimates, we will use a cluster of 7 4×2 server racks in an 8 tile pitch configuration, which would have 28 occupied tiles and 44 unoccupied tiles.
Finding servers per data center with data center square footage
To calculate how many servers are in a high tier data center, we will use Google’s Pryor Creek data center in Oklahoma. This data center is 980,000 sq ft according to DataCenter Knowledge, but Google does not disclose the size themselves.
This is a good example of a high tier data center because it is quite a bit more small than the largest data center, Switch in Tahoe NV, which is 7.2 million sq ft, but larger than a more common 300,000 sq ft data center.
To make this math a bit more easy, let’s round up to 1 million square feet.
Total sq ft: 1,000,000
Server room as percentage of total square footage: 1,000,000 (data center sq foot)* .65 (65% estimated portion dedicated for servers) = 650,000 sq ft
Tiles in the server room: 650,000 (server room sq ft) / 4 (sq ft per tile) = 162,500 tiles
Ratio of occupied tiles vs blank tiles: 28 / 44 = .636 (63.6% of room occupied by server racks)
Total occupied tiles vs total tiles in server room: 162,500 (tiles) * .636 (percent tiles occupied) = 103,409 occupied tiles
Average sized rack U height vs occupied tiles: 52(RU) / 2 (tiles) = 26 (rack units per occupied tiles) * 103,409 (occupied tiles) = 2,688,636 1U servers (given average U height is 52 units per rack)
With this math, we estimate that in a 1 million sq ft data center with 65% of the site being used for servers using only 52U racks, there can be 2,688,636 1U servers, 1,344,318 2U servers or 896,212 3U servers.
Finding servers per data center with kW per square footage
Coming up with an estimate solely using floor tiles unfortunately doesn’t tell the entire story. More often than not, data centers are restricted by their power capacity rather than square footage.
For example, the Switch Tahoe data center is the largest in the world in terms of square footage but is capped at 55kW per cabinet. With a total of 850 Megawatts (850,000 Kilowatts), this means that there can be 15,454 server racks at full capacity.
According vxchnge, a “typical” server rack uses 7 kW, and more higher powered racks use around 25 KW. It’s not likely that someone will use the entire 55kW per cabinet (server rack) offered by Switch, but we’ll use this number to reflect the worst case scenario in a data center.
850,000 kW / 7 kW = 121,428 racks * 52(U) = 6,314,256 1U servers
850,000 kW / 25 kW = 34,000 racks * 52(U) = 1,768,000 1U servers
850,000 kW / 55kW = 15,454 racks * 52(U) = 803,608 1U servers
To summarize, a data center with 850 Megawatts of capacity can run around 6,314,256 low powered 1U servers, 1,768,000 mid powered 1U servers or 803,608 high powered servers in a 52U Rack.
This number scales down depending on how much energy each server uses or how large the racks are.