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Liquid Cooling
Liquid cooling’s here to stay
Liquid Cooling is starting to make its presence felt in data
centers as air cooling is not up to the task of dissipating the heat generated
by modern rack equipment. Abhinav Singh reports
 At
the DataCenter-Dynamics 2007 conference held recently in New York attendees
were asked whether they had implemented liquid cooling in their data center.
Only three hands went up in response to that question. In India, however, this
trend has found some takers. Sun Microsystems in Bangalore is using liquid cooling
for its data center in a big way and the company has adopted a solution from
APC that is based on chilled water. Other companies are expected to follow Sun’s
lead as large data centers are being re-designed to address the problem of excess
heat buildup.
Today many a large data center is looking at including liquid cooling as an
option as many companies are running out of room to ventilate racks. The next
step is to put liquid cooling next to the rack. Improved energy efficiency is
just one of the many benefits that this technology brings to the table and it’s
a lot easier to pump liquid, than air, to where it’s needed.
Liquid cooling is not new; it’s been used from the days
of the mainframe. Mainframes generated a lot of heat. So much so that it was
too much for air cooling to handle. Air cooling is not as effective as liquid
cooling for the same volume. As computers and servers become smaller and their
density goes up, at some point we will not be able to cool data center racks
with air anymore. They will have to be cooled with liquid directly. That’s
what happened in the case of the mainframes where vendors were forced to resort
to liquid cooling.
- Water is more than 3,500 times more efficient
than air in transporting heat (thermal carrying capacity).
- Chemical refrigerants can be used instead
of water. One advantage: They evaporate and do not cause floods if they
leak.
- Cooling the ambient air in a room is the
standard, but it is
inefficient.
- Getting cold air to the places where heat
is generated requires fans to push the air around. The fans themselves
consume a lot of the power that is used for cooling.
- Most data centers already have water pipes
feeding wall-mounted A/C. Concerns about leaks can be addressed by water
cooling systems that are carefully designed to mitigate leaks.
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Hello, liquid; goodbye, air
In the past there has been an inexorable rise in microprocessor speeds. The
nasty side effects of denser CPUs with higher clock speeds is the result of
an electronic form of friction—electrical signals travel over wires with
resistive and capacitive loads—a process requiring energy that is ultimately
dissipated as heat. The faster signals are switched, the more the power that
is required. To address this problem liquid cooling has emerged as a better
alternative.
According to Rittal, water is 3,500 times more efficient at transferring and
transporting heat than plain old air. That is why vendors have developed a variety
of products that brings liquid’s heat transfer advantages closer to the
heat source--data center equipment.
In the case of air-cooling, the greatest difficulty presented
by room air conditioning is the even distribution of air around all computer
components. It is extremely difficult to create the correct air supply conditions
at every point in the room, for every IT component that has to be cooled. Air
carries less heat than liquid does for the same volume and as systems become
smaller in a data center with the goal of improving space utilization, density
goes up and it cannot be cooled with just air anymore and would have to be cooled
with liquid directly.
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 "Water
is an efficient medium to cool as the efficiency of heat transfer is much
higher than that of air and it is efficient for denser environments"
- James Mouton
Senior Vice President & GM, Industry Standard Servers, HP
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 "Liquid
cooling has the ability to [handle] high heat loads in the data center.
The power consumption [of this technology] is low"
- Mallikarjun S
Senior Manager-Marketing,
Rittal India Pvt Ltd
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 "The
fear that water will leak in the data centre is gradually fading as data
centers are preconfigured in such a way that the admin is immediately
notified in case of a leak"
- Pankaj Sharma
President, ISB Region,
APC-MGE
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James Mouton, Senior Vice President & GM, Industry Standard
Servers, HP said, “Although there isn’t a mad rush towards liquid
cooling in the data centers, water is a very efficient medium to cool the data
center as the efficiency of heat transfer is much higher than [that of] air
and is efficient for denser environments.” Those enterprises that have
access to excess amounts of chilled water prefer to use chillers to cool their
data centers with the help of water. They pre-configure their data centers for
liquid cooling.
Mallikarjun S, Senior Manager-Marketing, Rittal India Pvt Ltd added, “Liquid
cooling has the ability to [handle] high heat loads in the data center. [At
the same time] the power consumption [of this technology] is low. Air-cooling
is challenging as it has even distribution of air around all components in the
data center and hence it is difficult to create the correct air supply conditions
at every point in the room. In sharp contrast, enclosure cooling using a liquid
can create a micro climate within each rack.”
| Data centers are predominantly air cooled today.
However, with rack heat loads steadily rising, delivering adequate airflow
rates or sufficient chilled air is becoming harder to do. These trends in
the heat load generated from IT equipment can have detrimental side effects,
such as decreased equipment availability, wasted floor space, and inefficient
cooling. The upshot is that there is a clear need to implement liquid cooling
solutions. The overall goals of these implementations include aspects such
as transferring as much waste heat to the facility liquid cooling loop as
possible, reducing the overall volume of airflow needed by the racks, and
reducing processor temperatures in such a manner that increased compute
performance can be achieved.
Liquid cooling can also help overcome the limitations
imposed by thermal issues while still meeting the demand for higher density.
Liquid cooling can eliminate up to 50 percent of a rack’s total heat
load. Utilizing a completely non-conductive, inert fluid, it captures
heat from inside the blade chassis via liquid phase change, and then transports
it completely out of the data center using existing chilled or condenser
water lines.
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Liquid cooling helps increase server density
A migration from air to direct liquid cooling is being used to address surging
data center energy costs and allow the power densities of servers to continue
to increase into the next decade. Some data center managers may not fully grasp
the problem, because over the past eight years, server performance has increased
by a factor of 75 while performance per watt of power has increased 16 times
and the data centers are using more number of processors than ever. Meanwhile,
the power density of equipment has increased to the point where power and cooling
play a critical role. That creates two problems. First, energy costs are spiraling
upward. Many data center managers don't see that today, because their power
use isn't metered separately and isn't part of the IT budget. As costs rise,
that's likely to change, forcing IT to retrofit data centers to the new reality.
If you want to know what the heat coming off a 30 kilo watt rack feels like,
turn your broiler oven on full blast and open the door. It is being estimated
that the current air-cooling technologies can perhaps handle rack cooling till
mid 30 kilo watt. But there are estimates that 50 kilo watt racks could be a
reality within five years and that is where liquid cooling will play a critical
role as it will be able to cool denser environments easily than air cooling.
All the heat will have to be removed from the data center, which is one reason
why data center infrastructure costs per server have risen. In fact, while the
cost of server hardware has remained flat or declined slightly, the cost of
the data center infrastructure to support a server over a three-year life span
exceeded the hardware cost back.It is expected that in 2007 the cost of energy
(power and cooling) required per server, amortized over that same three years,
has pulled even with the equipment cost. By 2008, it will surpass it, becoming
the single largest component of server TCO. It is here that the liquid cooling
component will play a critical role as it will help in the direct cooling of
servers by piping liquid refrigerant or chilled water directly to components
within racks which is far more efficient than using air and will become a requirement.
More efficient designs will be able to cut cooling costs, which today can account
for more than half of data center energy per use. Best practices and optimizations
of existing infrastructure will be able to bring in immediate savings. On racks
approaching 30 kW, users are turning to spot-cooling systems that run liquid
refrigerant or chilled water to a heat exchanger that blows cool air from directly
above or adjacent to server racks. That's more efficient than room air- conditioning
units because the chilled air travels a shorter distance. These designs pipe
liquid coolant, already used by computer room air-conditioning units at the
outer edges of the data center, up to the racks themselves. It's not hard to
imagine extending those lines into the racks to deliver direct liquid cooling.
| In recent years, chip and server vendors have focused
on reducing power input and heat output. As data center gear purchases catch
up with the current generation of CPUs, heat and power loads are still increasing.
Liquid cooling is increasingly seen as the inevitable next step. According
to some vendors many of their customers are investigating liquid cooling
systems (above rack, in-row or in-rack etc.) and many are implementing these
solutions. New standards for liquid cooling systems are likely to spur faster
adoption. The American Society of Heating, Refrigerating and Air-Conditioning
Engineers (ASHRAE) recently published a book on data center liquid cooling
that could help promote standardization of the technology. One thing is
certain, demand for compute power will keep rising and heat is an unavoidable
byproduct of any compute activity. Liquid cooling is already present in
most data centers: chilled water systems are used to condition ambient air.
Standardized in-rack or on-chip fluid delivery
systems can greatly assist the goal of efficient and safe liquid cooling
in the data center, because such standards will create rules and best
practices as well as common interfaces between racks and cooling gear.
ASHRAE is working with large system OEMs such as Dell, HP, Sun and IBM
in this area. So far, it has issued a couple of manuals containing guidelines
for using liquid cooling with IT equipment.
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Efficient and economical
Jyothi Satyanathan, Vice President, Systems p, IBM India-South Asia said, “Liquid
cooling comes at a lesser cost when compared to air conditioners, as [the latter]
requires huge blowers, which add to the cost.
[Air conditioning] consumes more power. To remove 10 units of heat from a system
it requires more power than a liquid cooling system. We have many customers
in India who have been using liquid cooling in their data centers.” Lower
cost and superior power efficiency can be the major drivers for enterprises
to go in for liquid cooling in India. Ullas Sharma, Country Manager, Air Products,
Emerson Network Power Limited said, “It has been observed that if a customer
has additional capacities of water, then chillers are more power efficient when
compared to air cooled systems which require additional DC precision equipment
along with large fans and blowers which consume more power and require additional
investments.” However, it is a fact that the larger a data center the more
efficient liquid cooling is as a large dedicated chiller can help in cooling
a denser environment more efficiently.
Fading reservations
Customers were initially hesitant and believed that water posed a serious threat
in terms of leakages and moisture in the data center that could harm systems.
Other concerns included piping worries and additional equipment requirements.
Worries about condensation, the dew point in the room, and the chemistry of
water also existed. Pankaj Sharma, President, ISB Region, APC-MGE said, “The
fear that water will leak in the data centre is gradually fading as data centers
are pre-configured in such a way that it is immediately notified in case there
is a leakage. We have brought in pipes in our solution that are joint less and
it completely helps in eliminating any possibilities of leakage.” Similarly
Rittal also has a solution, which can help in cooling a system internally using
water and the pipes are designed in such a way that it eliminates any possibilities
of leakage. It is a fact that liquid cooling has been an effective mechanism
to cool chips and processors inside a system when compared to air. Rittal has
developed solutions in this space and many vendors are doing R&D in this
area.
Vendors such as APC and Rittal are popularizing the concept of liquid cooling
in data center. Rittal has around 1,500 customers worldwide for its liquid cooling
products and is now marketing its liquid cooling solution in a big way in the
Indian market as well. Other vendors such as Emerson, IBM and HP have different
approaches on liquid cooling and have mixed opinions on the subject.
| Vendor |
Solution |
Rittal
India
RiMatrix 5 |
The solution is called RiMatrix 5. It is an integrated,
scalable solution for both small businesses and large enterprises. Rimatrix
5 can effectively handle complex applications with faster processors and
round the clock information.
- RiMatrix 5 offers cooling for high performance
servers
- Monitoring and remote management are supported
for transparency and security in the data centre
- Modular power ensures maximum efficiency
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| HP
Modular Cooling System |
The HP Modular Cooling System is a self-cooled rack
for high density deployments in the data center.
- It is designed to support a full load
of blade servers, with a maximum configuration of 30 kWh.
- The unit can provide more than 2,700 CFM
(Cubic Feet per Minute) of cool air distributed along the full height
of the rack, cooling all servers evenly.
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APC
In Row RC |
InfraStruXure In Row RC is a computer
room air conditioning system designed for installation in the row to maximize
cooling. The unit captures heat directly from the hot aisle and distributes
cool air ensuring that equipment temperatures are constantly held to set
point condition. |
A definite shift
After a thorough probe by Express Computer we found that there is a definite
shift towards liquid cooling but hesitations persist in the minds of IT managers
to move forward with liquid cooling systems in the data center. However, there
has been a strong vendor push to popularize liquid cooling, as it is an effective
way to cool denser data center environments. That said, the future appears bright
for liquid cooling in the data centers in India and the technology is here to
stay.
abhinav.singh@expressindia.com
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