8 ms·

Liquid cooling next-gen servers getting hands-on

55 points by vanburen 5y ago

cyberge99 5y ago
I think datacenters will opt for more ARM architectures before introducing liquid at scale. Things like Gravitron and Apple Silicon are changing the landscape there.
- sudosysgen 5y ago
  Graviton and Apple Silicon still don't offer significant performance per watt improvements versus EPYC. I don't think it will make or break the need for liquid cooling.
- atty 5y ago
  I’m pretty sure AMD offers perf/watt that is in the ballpark of ARM chips, and I’m guessing Intel, if they ever get on a similar process node again, will be able to get close. None of that changes the need for accelerators though. Nvidia et al want to make the biggest chips they can, and at some point that means water cooling.
- PragmaticPulp 5y ago
  The article is mostly about cooling high power, GPU-like accelerator units that consume 400-600W or more. Even with power efficient architectures, the push to scale up core count and increase density will still drive toward more liquid cooling.
- ksec 5y ago
  You still have a 280W CPU, instead of 64 Core you now have 128. And if thermals permits they would like 128 x86 Core or 256 ARM Core. Samsung just announced their work of 7xxGB of DDR5 per stick. With a future roadmap of 1TB per stick at a request of hyperscaler. Along with 400W or 500W GPU. And when you have many new packaging technology where each die could be a 100W TDP you quickly run into all sort of thermals limits. And there are all sort of HPC and niche that wants super powerful Server.
jeffbee 5y ago
It seems odd to discuss liquid cooling but spend the first part of the article talking about AC PDUs and their issues. If you are able to use liquid cooling in a data center, aren’t you also sophisticated enough for modern DC to point-of-load? I can see why supermicro needs to pursue this direction, but it seems inevitable that their business will get eaten up by OCP and integration at the rack, row, and building level.
devwastaken 5y ago
I'm curious why liquid cooling for computers still uses compression fittings and other odd methods. Compression fittings are widely out of favor due to their tendency to leak, and nowadays everything is copper, pex, or metal+flared fittings. I wonder if there's a PC running PEX-A for tubing. Further thoughts: Brake lines use flared fittings, with either metal tubing or plastic tubing with metal ends. Uses a special bolt that allows liquid through the pipe to enter the caliper, and is removable. I would imagine something like that could work to make the lines to the individual servers serviceable without relying on flaky plastic "quick connects".
- lazide 5y ago
  Compression fittings are generally more convenient and cost effective than Pex or copper in small volumes and with little experience. The only downside as you note is leaks if someone doesn’t do them right (or as time passes), but that tends to be more of problem at higher household service line pressures (60+ psi) If it is a low pressure recirculation system, you can get by with almost no tools and most people if they read instructions at all probably won’t mess it up bad enough to have a leak. The brake line connectors could be interesting, but aren’t likely to work well stock - brakes are very low flow, high pressure as they are ‘dead ended’ hydraulic systems used to transfer force, not loops for cooling purposes. Also those bolts can work loose, and then you have leaks. Brakes require experienced technicians or people die, so folks working on brakes tend to be the more qualified and experienced mechanics, and they make sure to torque to spec, clean surfaces, do proper prep, etc. which is not what you want to have to worry about from an idiot proofing perspective.
  - heelix 5y ago
    Man, if only copper was easy. One of the gotchas is most connectors for CPU, graphics cards, and chipsets tend to use the G1/4" ends up having metric on the other side. 12mm or 13mm. Most copper pipe is .5", which works out to about 12.7mm. You have to be really picky with couplers if you want to use copper. PTEG/Acrylic is less great for things that would be banged around and a pain, compared to if you know how to actually do copper.
titzer 5y ago
Cool stuff. I remember seeing liquid cooling solutions that immersed the entire system in some non-conductive fluid, like mineral oil. Of course, that's a bit messy, but I wonder if all components were designed to be immersed, whether it'd be feasible to consider the entire server enclosure as the watertight unit, e.g. in a rack, rather than hoses to individual servers.
- toast0 5y ago
  Immersing the rack as a unit means commiting to servicing the rack as a unit. Some organizations do that. Bring the rack up, do a burn in test, then run it until enough bits are broken that it makes sense to take the whole thing down to swap bits or until it's obsolete enough to justify replacing the whole thing. But a lot of organizations want to replace storage or ram or ?? as it fails without turning off the whole rack. Would bring more meaning to the words 'draining' a server/rack/data center though. Actually reading the article, they have immersion chambers which look more or less like a rack rotated 90 to be horizontal. Which means you can pull a rack mount server out vertically to service it, but it also takes up a lot more floorspace (at least 3x to my eye), which reduces density. If you were OK with reduced density, you could leave your racks 2/3rds empty or use 2U servers instead of 1U servers, etc. Power and cooling requirements are already the bottleneck for most datacenters rather than floorspace, and liquid cooling doesn't really help a lot there (unless you can pump your working fluid outdoors, but usually it's just dumping the heat elsewhere in the room more effectively, sometimes with more power for a pump than for fans).
  - elihu 5y ago
    I once saw a setup with a whole rack laid down on its back in a tub of mineral oil, like you describe. You could slide individual servers up and set them on the top of the enclosure, letting them drip down into the tub. Kind of messy, but not unreasonably so. (This was setup at SC'09 in Portland. I'm impressed that someone went to the trouble to set this thing up just for a few days of a conference.) The oil was actively pumped through a radiator with a fan. Part of the whole point of the system is that, since oil is a better coolant than air, they can run the whole system at a higher ambient temperature, like 80 or 90 degrees F instead of 70-ish. That could reduce energy costs quite a bit. I'm not sure if the oil goes bad eventually and has to be replaced; I could see that being expensive if there isn't a simple way to clean/recycle/reprocess it back into usable oil.
zamalek 5y ago
> need to handle cooling at >1kW/U I wonder if this waste heat could be used to power active/phase change cooling.
- icegreentea2 5y ago
  The challenge is that it's really low grade heat (< 100C). DC waste heat would probably find its best use in district heating applications (though I did read about some cases still using a heat pump to boost the waste heat stream even higher - still for district heating though).
opwieurposiu 5y ago
A lot of high power plasma processing equipment is water cooled. RF and DC generators, matches, etc. Stuff that requires a coax cable as thick as your arm. The switch from air to water cooling happens around .5-1Kw, this is the same range they seem to be targeting for datacenter stuff. Aside from leaks, the building maintenance staff really needs to stay on top of the cooling water chemistry. Cooling loops tend to make slime and if you let it get out of control it clogs up everything and becomes a real problem to clean.
KaiserPro 5y ago
> Data center liquid cooling is going to happen I mean yeah, but I doubt its going to be mainstream anytime soon. At the moment its cheaper to just use forced air, and yolo it. Running at half density is expensive, but not as expensive as backfilling everything with liquid cooling. Also given that we've been able to run 2 socket blades at full bore without liquid cooling kinda suggests its not actually needed. Having radiators on the front/back of the rack directly works really well. We had it on our render farm. combine that with enforced hot isle/cold isle and you can reduce the need for aircon dramatically, without multiplying your leak risk by at least 96 times. The massive problem here is that its really difficult to hotswap anything. Those cooling pipes need to be removed before you can pull out the server. Unless they are self sealing (like hydrolic lines) then you need to drain the loop first. That costs a shitload of money at scale.
- ksec 5y ago
  >The massive problem here is that its really difficult to hotswap anything. And this problem has been there since Day 1 ( For well over a decade ). And no one seems to have solve it. It make sense if you treat the whole Rack as a single entity with water cooling. But for individual server I still dont understand how and why liquid cooling could benefits.
  - mey 5y ago
    The problems that FAANG have aren't the problems most of us have. Edit: That don't work for those companies. Different levels of scale certainly. https://xkcd.com/1737/ https://xkcd.com/1737/
  - sandworm101 5y ago
    >> I still dont understand how and why liquid cooling could benefits. Because liquid cooling is only a marginal benefit for current hardware, hardware designed to be air cooled. If liquid cooling becomes a norm we should start seeing hardware designed with the expectation of liquid cooling. That could mean greater component density and greater power concentration --> greater speeds. One wonders what CPUs would be like if they were designed with the expectation of liquid cooling, water within a millimetre from the heat source rather than the metal heat spreaders that currently top most chips. How many fans are in a modern server rack? Liquid cooling could theoretically replace all of those with one moving part, one pump impeller.
20100thibault 5y ago
Liquid cooling also enables heat recovery and free cooling all year long. Here's a project using liquid cooling to recover energy from Data centers to heat greenhouses. https://www.qscale.com/ https://www.qscale.com/
bob1029 5y ago
Direct liquid cooling makes a shitload of sense from a purely academic standpoint. At what point in power density would it not even matter if the datacenter was at meat locker temperatures? I feel like we are getting pretty damn close. The efficiency gains at scale must be really good. I can see why this is not super popular though.
jmcguckin 5y ago
One place i worked used flourinert to cool the circuit cards of a integrated circuit tester. Each card has a 'cold plate' where the outside of the cold plate has a brass tube brazed to the plate in a serpentine pattern leading to two quick disconnect connectors that automatically engage/disengage when the card in inserted or removed from the card cage. The other side of the cold plate (the 'inside') has spring loaded fingers to pull the heat away from chips. We had some chips that dissipated over 100W. This worked great - you'd lose maybe 1 drop of fluid per card insertion, etc. We used flourinert, but DI water, mineral oil or water with ethylene glycol could be used as well.
bastardoperator 5y ago
Data centers have been using chilled water to cool air for a long time. It would be interesting to see cooling delivered directly to the CPU/GPU from a/the chiller.
- sschueller 5y ago
  No thanks, the equinix DC I have dealt with has had so many chiller outages I am glad that the fans were able to keep the temp low enough to prevent damage. If I lost all cooling the equipment would literally be toast.
  - wmf 5y ago
    Almost no server equipment will be damaged by loss of cooling; it will shut down before damage occurs.
    - sschueller 5y ago
      Repeat overheating even with auto shutoff can result in solder joints going bad and reducing the life span of hw. Additionally not all components that are overheating will cause on auto shutoff.
ChuckMcM 5y ago
I cannot help but chuckle at how what is old is new again here. In the 70's and early 80's all of IBM's mainframes supported liquid cooling. Basically when a computer "uses" X kW of power it really means that it generates that many kW of heat while it is operating. Removing heat at scale has been a thing for a long time. And what was alluded to in the video is the thermal mass of 'air' kind of sucks. So the old design of chilling air down to 67 degrees and filling a room with that air so that it can circulate around electronics putting out prodigious amounts of heat, and then collected and re-cooled, is not nearly as efficient as one would like. Cooling water, piping it to the heat exchanger in the back door of the rack and then (unlike the video's idea) sucking air through it first, and then pushing the cooled air over the electronics to 're-heat' it, works better. Then you don't really care what temperature the air in the data center itself is as long as the heat exchanger can remove 'x' watts of heat from it before it gets blown over the computers. Suck air in from the floor (the coolest air) and blow it out the top (where it continues on to the ceiling). Still, that only doubles the power capacity of the racks (maybe 2.5x if the heat exchanger is filled with actively chilled water) Prior to heat exchanger doors people would have "cold" aisles and "hot" aisles. The cold air from the CRAC units would come up from the floor behind the servers, get sucked through them and exhausted forward into the "hot" aisle. There is a whole little mini industry of "cold air containment" which has stuff to build doors/covers for the cold aisle so that all of that air is sucked through servers.
alberth 5y ago
What makes this time different? I've literally heard this is coming to datacenter for 20 YEARS and it hasn't yet. Liquids like mineral oil, etc to be the cooling agent yet it never gains measured adoption. And with so much of servers now being centrally managed by just a few major cloud providers (AWS, Azure, etc) - unless you can break into those few accounts - how will this time be any different than the past? From 2003: https://www.hitachi.com/New/cnews/E/2003/0217/index.html https://www.hitachi.com/New/cnews/E/2003/0217/index.html
- kllrnohj 5y ago
  > Liquids like mineral oil, etc to be the cooling agent yet it never gains measured adoption. I've never seen a serious attempt to do mineral oil cooling outside of funny gag setups. It was never really pitched as a future of cooling. There's other attempts at other liquids for submersion cooling, but that always seems like a bit of a stretch. Beyond that, liquid cooling has taken over. That Hitachi post, for example, seems to be about AIOs which are now very common on desktops with the AIO market exploding over the last ~5 years. Nearly every laptop also employs a form of "liquid cooling" these days with either heatpipes or vapor chambers. As for "what makes this time different" for the datacenter, well heat density continues to rise. >100 CPU cores per 2U rack are trivial to achieve now, and more are readily plausible. GPU accelerators are also more common than ever, and are pushing staggering power draws (like the 8x 400W NVIDIA A100 in a single 4U chasis the article talks about). You can keep spending more power on fans, but there's diminishing returns there not to mention the power consumption of the fans themselves becomes non-trivial.
Const-me 5y ago
Technically, the best solution is distribute. Specifically, compute stuff on user's own devices, as opposed to moving everything to these centralized clouds controlled by just a few large corporations. Too bad that's unlikely to happen.
- elihu 5y ago
  The "cloud" can be far more energy efficient than personal computing devices, and geographically distributed computation has costs as well, if you're doing computation that requires a lot of data that isn't all in one place. I think keeping one's own data on one's own local hardware has other significant privacy/security/control benefits, but energy efficiency is probably not among them.
  - Const-me 5y ago
    More than 50% personal devices are phones and tablets. They are using ARM CPUs notable for power efficiency (because battery powered). More than 50% of computers being sold are laptops. Guess what, these mobile CPUs are notable for power efficiency, because battery powered. Only a minority of users (myself included) have desktop computers with FLOPS/watt figure that’s worse than massively multicore server-targeted AMD64 processors used by cloud providers. Clouds are slowly transitioning to ARM64 as well (I have personally shipped a cloud app working on Ampere Altra CPUs) but still, so far majority of them are using faster but less efficient AMD64 CPUs. Another thing, moving data costs energy. Inside each CPU core, you have like 400GB/sec bandwidth to the caches with no energy overhead. Moving data to/from system RAM takes way more electricity. Moving that data to/from a server on another end of the world takes way more electricity than that: the wires and optical cables are long, and there’re many routers/amplifiers/other hardware in between. And another thing. Personal devices have limited compute power. This creates incentive for developers to optimize their code. If your stuff is too slow, users with low-end devices will be unhappy. With unlimited compute power of the clouds, it sometimes makes sense to neglect that and just throw resources at the problem.
swayvil 5y ago
Why is that guy wearing a mask? Either servers are infectious or wearing a mask is now just "expected". Do any of you do a doubletake when you see people on tv without a mask? Have you noticed characters in cartoons wearing masks? Check out the weather frog, sitting alone in the middle of a forest, wearing a mask. This how we become Morlocks.
Havoc 5y ago
Is there a reason the ai accelerators etc can’t just be parked in the polar circle? Not every workload is that latency sensitive presumably

55 points by vanburen 5y ago

I think datacenters will opt for more ARM architectures before introducing liquid at scale. Things like Gravitron and Apple Silicon are changing the landscape there.

sudosysgen 5y ago
Graviton and Apple Silicon still don't offer significant performance per watt improvements versus EPYC. I don't think it will make or break the need for liquid cooling.
atty 5y ago
I’m pretty sure AMD offers perf/watt that is in the ballpark of ARM chips, and I’m guessing Intel, if they ever get on a similar process node again, will be able to get close. None of that changes the need for accelerators though. Nvidia et al want to make the biggest chips they can, and at some point that means water cooling.
PragmaticPulp 5y ago
The article is mostly about cooling high power, GPU-like accelerator units that consume 400-600W or more. Even with power efficient architectures, the push to scale up core count and increase density will still drive toward more liquid cooling.
ksec 5y ago
You still have a 280W CPU, instead of 64 Core you now have 128. And if thermals permits they would like 128 x86 Core or 256 ARM Core. Samsung just announced their work of 7xxGB of DDR5 per stick. With a future roadmap of 1TB per stick at a request of hyperscaler. Along with 400W or 500W GPU. And when you have many new packaging technology where each die could be a 100W TDP you quickly run into all sort of thermals limits. And there are all sort of HPC and niche that wants super powerful Server.

jeffbee 5y ago

It seems odd to discuss liquid cooling but spend the first part of the article talking about AC PDUs and their issues. If you are able to use liquid cooling in a data center, aren’t you also sophisticated enough for modern DC to point-of-load? I can see why supermicro needs to pursue this direction, but it seems inevitable that their business will get eaten up by OCP and integration at the rack, row, and building level.

devwastaken 5y ago

I'm curious why liquid cooling for computers still uses compression fittings and other odd methods. Compression fittings are widely out of favor due to their tendency to leak, and nowadays everything is copper, pex, or metal+flared fittings. I wonder if there's a PC running PEX-A for tubing. Further thoughts: Brake lines use flared fittings, with either metal tubing or plastic tubing with metal ends. Uses a special bolt that allows liquid through the pipe to enter the caliper, and is removable. I would imagine something like that could work to make the lines to the individual servers serviceable without relying on flaky plastic "quick connects".

lazide 5y ago
Compression fittings are generally more convenient and cost effective than Pex or copper in small volumes and with little experience. The only downside as you note is leaks if someone doesn’t do them right (or as time passes), but that tends to be more of problem at higher household service line pressures (60+ psi) If it is a low pressure recirculation system, you can get by with almost no tools and most people if they read instructions at all probably won’t mess it up bad enough to have a leak. The brake line connectors could be interesting, but aren’t likely to work well stock - brakes are very low flow, high pressure as they are ‘dead ended’ hydraulic systems used to transfer force, not loops for cooling purposes. Also those bolts can work loose, and then you have leaks. Brakes require experienced technicians or people die, so folks working on brakes tend to be the more qualified and experienced mechanics, and they make sure to torque to spec, clean surfaces, do proper prep, etc. which is not what you want to have to worry about from an idiot proofing perspective.
- heelix 5y ago
  Man, if only copper was easy. One of the gotchas is most connectors for CPU, graphics cards, and chipsets tend to use the G1/4" ends up having metric on the other side. 12mm or 13mm. Most copper pipe is .5", which works out to about 12.7mm. You have to be really picky with couplers if you want to use copper. PTEG/Acrylic is less great for things that would be banged around and a pain, compared to if you know how to actually do copper.

titzer 5y ago

Cool stuff. I remember seeing liquid cooling solutions that immersed the entire system in some non-conductive fluid, like mineral oil. Of course, that's a bit messy, but I wonder if all components were designed to be immersed, whether it'd be feasible to consider the entire server enclosure as the watertight unit, e.g. in a rack, rather than hoses to individual servers.

toast0 5y ago
Immersing the rack as a unit means commiting to servicing the rack as a unit. Some organizations do that. Bring the rack up, do a burn in test, then run it until enough bits are broken that it makes sense to take the whole thing down to swap bits or until it's obsolete enough to justify replacing the whole thing. But a lot of organizations want to replace storage or ram or ?? as it fails without turning off the whole rack. Would bring more meaning to the words 'draining' a server/rack/data center though. Actually reading the article, they have immersion chambers which look more or less like a rack rotated 90 to be horizontal. Which means you can pull a rack mount server out vertically to service it, but it also takes up a lot more floorspace (at least 3x to my eye), which reduces density. If you were OK with reduced density, you could leave your racks 2/3rds empty or use 2U servers instead of 1U servers, etc. Power and cooling requirements are already the bottleneck for most datacenters rather than floorspace, and liquid cooling doesn't really help a lot there (unless you can pump your working fluid outdoors, but usually it's just dumping the heat elsewhere in the room more effectively, sometimes with more power for a pump than for fans).
- elihu 5y ago
  I once saw a setup with a whole rack laid down on its back in a tub of mineral oil, like you describe. You could slide individual servers up and set them on the top of the enclosure, letting them drip down into the tub. Kind of messy, but not unreasonably so. (This was setup at SC'09 in Portland. I'm impressed that someone went to the trouble to set this thing up just for a few days of a conference.) The oil was actively pumped through a radiator with a fan. Part of the whole point of the system is that, since oil is a better coolant than air, they can run the whole system at a higher ambient temperature, like 80 or 90 degrees F instead of 70-ish. That could reduce energy costs quite a bit. I'm not sure if the oil goes bad eventually and has to be replaced; I could see that being expensive if there isn't a simple way to clean/recycle/reprocess it back into usable oil.

zamalek 5y ago

> need to handle cooling at >1kW/U I wonder if this waste heat could be used to power active/phase change cooling.

icegreentea2 5y ago
The challenge is that it's really low grade heat (< 100C). DC waste heat would probably find its best use in district heating applications (though I did read about some cases still using a heat pump to boost the waste heat stream even higher - still for district heating though).

opwieurposiu 5y ago

A lot of high power plasma processing equipment is water cooled. RF and DC generators, matches, etc. Stuff that requires a coax cable as thick as your arm. The switch from air to water cooling happens around .5-1Kw, this is the same range they seem to be targeting for datacenter stuff. Aside from leaks, the building maintenance staff really needs to stay on top of the cooling water chemistry. Cooling loops tend to make slime and if you let it get out of control it clogs up everything and becomes a real problem to clean.

KaiserPro 5y ago

> Data center liquid cooling is going to happen I mean yeah, but I doubt its going to be mainstream anytime soon. At the moment its cheaper to just use forced air, and yolo it. Running at half density is expensive, but not as expensive as backfilling everything with liquid cooling. Also given that we've been able to run 2 socket blades at full bore without liquid cooling kinda suggests its not actually needed. Having radiators on the front/back of the rack directly works really well. We had it on our render farm. combine that with enforced hot isle/cold isle and you can reduce the need for aircon dramatically, without multiplying your leak risk by at least 96 times. The massive problem here is that its really difficult to hotswap anything. Those cooling pipes need to be removed before you can pull out the server. Unless they are self sealing (like hydrolic lines) then you need to drain the loop first. That costs a shitload of money at scale.

ksec 5y ago
>The massive problem here is that its really difficult to hotswap anything. And this problem has been there since Day 1 ( For well over a decade ). And no one seems to have solve it. It make sense if you treat the whole Rack as a single entity with water cooling. But for individual server I still dont understand how and why liquid cooling could benefits.
- mey 5y ago
  The problems that FAANG have aren't the problems most of us have. Edit: That don't work for those companies. Different levels of scale certainly. https://xkcd.com/1737/ https://xkcd.com/1737/
- sandworm101 5y ago
  >> I still dont understand how and why liquid cooling could benefits. Because liquid cooling is only a marginal benefit for current hardware, hardware designed to be air cooled. If liquid cooling becomes a norm we should start seeing hardware designed with the expectation of liquid cooling. That could mean greater component density and greater power concentration --> greater speeds. One wonders what CPUs would be like if they were designed with the expectation of liquid cooling, water within a millimetre from the heat source rather than the metal heat spreaders that currently top most chips. How many fans are in a modern server rack? Liquid cooling could theoretically replace all of those with one moving part, one pump impeller.

20100thibault 5y ago

Liquid cooling also enables heat recovery and free cooling all year long. Here's a project using liquid cooling to recover energy from Data centers to heat greenhouses. https://www.qscale.com/ https://www.qscale.com/

bob1029 5y ago

Direct liquid cooling makes a shitload of sense from a purely academic standpoint. At what point in power density would it not even matter if the datacenter was at meat locker temperatures? I feel like we are getting pretty damn close. The efficiency gains at scale must be really good. I can see why this is not super popular though.

jmcguckin 5y ago

One place i worked used flourinert to cool the circuit cards of a integrated circuit tester. Each card has a 'cold plate' where the outside of the cold plate has a brass tube brazed to the plate in a serpentine pattern leading to two quick disconnect connectors that automatically engage/disengage when the card in inserted or removed from the card cage. The other side of the cold plate (the 'inside') has spring loaded fingers to pull the heat away from chips. We had some chips that dissipated over 100W. This worked great - you'd lose maybe 1 drop of fluid per card insertion, etc. We used flourinert, but DI water, mineral oil or water with ethylene glycol could be used as well.

bastardoperator 5y ago

Data centers have been using chilled water to cool air for a long time. It would be interesting to see cooling delivered directly to the CPU/GPU from a/the chiller.

sschueller 5y ago
No thanks, the equinix DC I have dealt with has had so many chiller outages I am glad that the fans were able to keep the temp low enough to prevent damage. If I lost all cooling the equipment would literally be toast.
- wmf 5y ago
  Almost no server equipment will be damaged by loss of cooling; it will shut down before damage occurs.
  - sschueller 5y ago
    Repeat overheating even with auto shutoff can result in solder joints going bad and reducing the life span of hw. Additionally not all components that are overheating will cause on auto shutoff.

ChuckMcM 5y ago

I cannot help but chuckle at how what is old is new again here. In the 70's and early 80's all of IBM's mainframes supported liquid cooling. Basically when a computer "uses" X kW of power it really means that it generates that many kW of heat while it is operating. Removing heat at scale has been a thing for a long time. And what was alluded to in the video is the thermal mass of 'air' kind of sucks. So the old design of chilling air down to 67 degrees and filling a room with that air so that it can circulate around electronics putting out prodigious amounts of heat, and then collected and re-cooled, is not nearly as efficient as one would like. Cooling water, piping it to the heat exchanger in the back door of the rack and then (unlike the video's idea) sucking air through it first, and then pushing the cooled air over the electronics to 're-heat' it, works better. Then you don't really care what temperature the air in the data center itself is as long as the heat exchanger can remove 'x' watts of heat from it before it gets blown over the computers. Suck air in from the floor (the coolest air) and blow it out the top (where it continues on to the ceiling). Still, that only doubles the power capacity of the racks (maybe 2.5x if the heat exchanger is filled with actively chilled water) Prior to heat exchanger doors people would have "cold" aisles and "hot" aisles. The cold air from the CRAC units would come up from the floor behind the servers, get sucked through them and exhausted forward into the "hot" aisle. There is a whole little mini industry of "cold air containment" which has stuff to build doors/covers for the cold aisle so that all of that air is sucked through servers.

alberth 5y ago

What makes this time different? I've literally heard this is coming to datacenter for 20 YEARS and it hasn't yet. Liquids like mineral oil, etc to be the cooling agent yet it never gains measured adoption. And with so much of servers now being centrally managed by just a few major cloud providers (AWS, Azure, etc) - unless you can break into those few accounts - how will this time be any different than the past? From 2003: https://www.hitachi.com/New/cnews/E/2003/0217/index.html https://www.hitachi.com/New/cnews/E/2003/0217/index.html

kllrnohj 5y ago
> Liquids like mineral oil, etc to be the cooling agent yet it never gains measured adoption. I've never seen a serious attempt to do mineral oil cooling outside of funny gag setups. It was never really pitched as a future of cooling. There's other attempts at other liquids for submersion cooling, but that always seems like a bit of a stretch. Beyond that, liquid cooling has taken over. That Hitachi post, for example, seems to be about AIOs which are now very common on desktops with the AIO market exploding over the last ~5 years. Nearly every laptop also employs a form of "liquid cooling" these days with either heatpipes or vapor chambers. As for "what makes this time different" for the datacenter, well heat density continues to rise. >100 CPU cores per 2U rack are trivial to achieve now, and more are readily plausible. GPU accelerators are also more common than ever, and are pushing staggering power draws (like the 8x 400W NVIDIA A100 in a single 4U chasis the article talks about). You can keep spending more power on fans, but there's diminishing returns there not to mention the power consumption of the fans themselves becomes non-trivial.

Const-me 5y ago

Technically, the best solution is distribute. Specifically, compute stuff on user's own devices, as opposed to moving everything to these centralized clouds controlled by just a few large corporations. Too bad that's unlikely to happen.

elihu 5y ago
The "cloud" can be far more energy efficient than personal computing devices, and geographically distributed computation has costs as well, if you're doing computation that requires a lot of data that isn't all in one place. I think keeping one's own data on one's own local hardware has other significant privacy/security/control benefits, but energy efficiency is probably not among them.
- Const-me 5y ago
  More than 50% personal devices are phones and tablets. They are using ARM CPUs notable for power efficiency (because battery powered). More than 50% of computers being sold are laptops. Guess what, these mobile CPUs are notable for power efficiency, because battery powered. Only a minority of users (myself included) have desktop computers with FLOPS/watt figure that’s worse than massively multicore server-targeted AMD64 processors used by cloud providers. Clouds are slowly transitioning to ARM64 as well (I have personally shipped a cloud app working on Ampere Altra CPUs) but still, so far majority of them are using faster but less efficient AMD64 CPUs. Another thing, moving data costs energy. Inside each CPU core, you have like 400GB/sec bandwidth to the caches with no energy overhead. Moving data to/from system RAM takes way more electricity. Moving that data to/from a server on another end of the world takes way more electricity than that: the wires and optical cables are long, and there’re many routers/amplifiers/other hardware in between. And another thing. Personal devices have limited compute power. This creates incentive for developers to optimize their code. If your stuff is too slow, users with low-end devices will be unhappy. With unlimited compute power of the clouds, it sometimes makes sense to neglect that and just throw resources at the problem.

swayvil 5y ago

Why is that guy wearing a mask? Either servers are infectious or wearing a mask is now just "expected". Do any of you do a doubletake when you see people on tv without a mask? Have you noticed characters in cartoons wearing masks? Check out the weather frog, sitting alone in the middle of a forest, wearing a mask. This how we become Morlocks.

Havoc 5y ago

Is there a reason the ai accelerators etc can’t just be parked in the polar circle? Not every workload is that latency sensitive presumably