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From what I read and hear about datacenters, there are not too many server rooms which use water cooling, and none of the largerst datacenters use water cooling (correct me if I'm wrong). Also, it's relatively easy to buy an ordinary PC components using water cooling, while water cooled rack servers are nearly nonexistent.

On the other hand, using water can possibly (IMO):

  1. Reduce the power consumption of large datacenters, especially if it is possible to create direct cooled facilities (i.e. the facility is located near a river or the sea).

  2. Reduce noise, making it less painful for humans to work in datacenters.

  3. Reduce space needed for the servers:

    • On server level, I imagine that in both rack and blade servers, it's easier to pass the water cooling tubes than to waste space to allow the air to pass inside,
    • On datacenter level, if it's still required to keep the alleys between servers for maintenance access to servers, the empty space under the floor and at the ceiling level used for the air can be removed.

So why water cooling systems are not widespread, neither on datacenter level, nor on rack/blade servers level?

Is it because:

  • The water cooling is hardly redundant on server level?

  • The direct cost of water cooled facility is too high compared to an ordinary datacenter?

  • It is difficult to maintain such system (regularly cleaning the water cooling system which uses water from a river is of course much more complicated and expensive than just vacuum cleaning the fans)?

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6 Answers

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Water + Electricity = Disaster

Water cooling allows for greater power density than air cooling; so figure out the cost savings of the extra density (likely none unless you're very space constrained). Then calculate the cost of the risk of a water disaster (say 1% * the cost of your facility). Then do a simple risk-reward comparison and see if it makes sense for your environment.

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up vote 4 down vote

While we do have a few water-cooled racks (HP ones actually, don't know if they still make them) direct water cooling is a little old-school these days. Most new large data centres are being built with suction tunnels that you push your rack into, this then pulls the ambient air through and expels or captures-for-reuse the heat collected as it moves through equipment. This means no chilling at all and saves huge amounts of energy, complexity and maintenance, though it does limit systems to using very specific racks/sizes and requires spare rack space to be 'blanked' at the front.

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up vote 2 down vote

I think the short answer is that it adds considerable complexity. It's not so much an issue of space.

If you've got large quantities of water to deal with (piping, runoff, etc) you're adding a lot of risk... water and electricity don't mix well (or they mix too well, depending how you look at it).

The other issue with water is humidity. On a large scale, it's going to throw all your air conditioning systems for a loop. Then there's mineral buildup from evaporation, and no doubt tons of other things I didn't think of here.

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up vote 2 down vote

Water is a universal solvent. Given enough time, it will eat through EVERYTHING.

Water cooling would also add a considerable (and costly) level of complexity to a data center which you allude to in your post.

Fire suppression systems in most data centers do not contain water for a few, very specific reasons, water damage can be greater than fire damage in a lot of cases and because data centers are tasked with uptime (with backup generators for power, etc.), this means that it's pretty hard to cut power to something (in the event of a fire) to squirt water on it.

So can you imagine if you have some type of complex water cooling system in your data center, that gives up the ghost in the event of a fire?? Yikes.

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up vote 2 down vote

water should NOT be used for datacenter cooling but a mineral oil that mixes very well with electricity. see http://www.datacenterknowledge.com/archives/2011/04/12/green-revolutions-immersion-cooling-in-action/

even though the solution is new the technology is quite old, however making this type of change into existing datacenters it becomes very difficult, as you need to replace the existing racks with new type of racks ...

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I disagree sorry, we have water-cooled racks, I was there the day they were filled and it was purified regular water. – Chopper3 Apr 27 '11 at 14:59
wow - then how is this working ? - do you have details ? – silviud Apr 27 '11 at 15:02
They're HP-rebadged racks (no idea who the original manufacturer was, Rittal maybe?, they were selling them about 2 years ago but I'll look now to see if they still are. – Chopper3 Apr 27 '11 at 15:16
thanks - found one at h10010.www1.hp.com/wwpc/us/en/sm/WF06a/… ... look at the price ... – silviud Apr 27 '11 at 15:27
Yes, that's the one, not sure they still sell them in the UK where I am, never thought to look on the US site. We had a use for them in a confined space where we needed a LOT of servers. – Chopper3 Apr 27 '11 at 15:31
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up vote 0 down vote

Water cooled dater centres are very efficient and cost savings in energy provided you have purified water . however the dangers are more if they are in close contact. 1) moisture/ humidity levels
2) water aginst Electricity.

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Do you have any reference to corroborate water cooling being more efficient? Seems like it would take more energy to pump the water around then then use fans to expel it into the atmosphere. How would water in a closed loop cooling system affect moisture/humidity levels? – Chris S♦ Jun 27 '11 at 17:58
@Chris S, the heat transfer coefficient of air is 10 to 100 W/m2K where water is 500 to 10,000 W/m2K. This gives you a significant density advantage that you can then make up with a large heat exchanger elsewhere. Consider an automobile coolant system for a good parallel. – Jodie C Jul 14 '11 at 23:51
@Jodie, you have to put more energy into pumping the water around, and more energy into pushing extra air over that larger radiator. The radiator has to go somewhere. That extra energy has costs, as does the water cooling gear, higher maintenance. Also, the transfer coefficient applies within the medium; hopefully you aren't suggesting the CPUs and water come in direct contact. There's likely a containment device which has it's own conductivity ratings. There's more to efficiency than the thermal transfer coefficient of the selected medium. – Chris S♦ Jul 15 '11 at 1:17
@Chris S, No, you don't put more energy into it. The pumping costs are minimal, and the larger area of the heat exchanger means you don't need high power fans to push through dense fin arrangements. Part of the problem with aircooling equipment is that you have to force massive amounts of air through a narrow space that you are simultaneously trying to cram as much surface area into as you possibly can. This is one of the reasons heatpipe coolers are prevalent in desktops. Piling on 40mm 15krpm fans in a 1U adds up quick. – Jodie C Jul 15 '11 at 1:42
@Chris S, for instance at 4ea 40mm 20cfm fans per CPU you're looking at 35W just in fans, versus a single 120MM 105CFM at 6W. An Eheim 1048 is sufficient for a 135W TDP and consumes 10W of power. So now you're at 16W for a system with a higher efficiency. – Jodie C Jul 15 '11 at 1:46
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