Energy efficient data center
It is a well-known fact that the lion's share of expenses in the operation of data centers falls on the ventilation system of the server rooms. First, kilowatts indirectly go to heat the equipment, then the same kilowatts also go to reject the heat generated by the equipment. Often, the most effective way of cooling, heated server equipment, is atmospheric ventilation, without pre-cooling. Using the most widely cool air from outside, the data center owners receive significant energy savings, because the main energy consumption of ventilation systems are not for air delivery, but for its cooling. The ventilation method, in which air masses coming from outside, do not undergo additional processing, is called free ventilation.
It is obvious that the climate of each particular locality imposes its own limitations on the possibility of using the air selected from the atmosphere as a free cooling medium. First of all, it should be borne in mind that it can not be used everywhere and secondly not always, moreover, the air masses throughout the planet are not very homogeneous, which is a particularly critical factor, besides the air temperature, naturally, its humidity.
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The research group ASHRAE (abbreviation for the American Community of Engineers Heating and Cooling Ventilation Systems) has been working for many years on the study of the allowable range of air masses that can be used to cool equipment in data centers. A special subcommittee of this organization, which deals directly with the study of data centers, provided a report in which researchers came to an unambiguous conclusion. Increasing the temperature in the server room by just a few degrees, in comparison with the most commonly recommended range of 18-24 degrees, can significantly expand the geography and time periods for cooling data center equipment with atmospheric air, without additional mechanical manipulations with it. But the main condition, which by all means should have been met in the course of research, is that the savings on the data center energy costs should not expose the equipment to any risk, because its operating temperature range is very flexible.
But to what measure can this temperature be raised? Indeed, in the pursuit of profit, it is possible to jeopardize expensive equipment - say skeptics of the revision of standards. In this vein, the study of engineers at Google has become very interesting. Having in its assets a huge network infrastructure, for the company the issue of increasing temperatures was crucial for the effective conduct of its activities. First of all, researchers identified a “weak link” in the network bundle, which is most susceptible to failure. In this competition, with a serious margin, "hard drives" took the palm. They are the ones most exposed to high temperatures, in addition to this, they themselves are powerful generators of excess heat. After the subject was identified, various tests with whole batches of disks were used. Most of the tests showed that there is, of course, a connection between the temperature mode of the functioning of the disks and the occurrence of errors in their work, but not everything is as linear as it might seem.
According to the statistics presented, low operating temperatures (from 15 ° C to 30 ° C) can become no less dangerous for disks than the temperature regime of 45 ° C and higher.
In this context, we can recall the fact that data centers are not only network hardware, but also living people, without which all this equipment is nothing more than highly technological scrap metal. According to current sanitary norms (GOST 30494—2011), for example, the maximum allowable temperature in public, non-residential premises can reach 31 o C. By the way, this tolerance is also significantly higher than the recommended temperature range in server rooms.
The research group ASHRAE, during its existence, has already revised the recommended operating temperature range in the server room three times and each time the revision was in the direction of its increase. The chronology of these decisions 2004, 2008, 2011, apparently now is the time, without violating the time step, to wait again for another such decision. In addition to the temperature range, the humidity of the air circulating in the data center is an important factor. The relationship between moisture and air temperature is inseparable parameters. Although now there are already new data centers where these characteristics are put under tight control, for many previously built data centers this is a significant foundation for modernization.
According to the prepared specification from ASHRAE, there are three modes of equipment operation with different physical properties of air masses:
Recommended: environmental conditions that provide high performance and uninterrupted operation of equipment.
Valid: equipment operation mode is carried out with parameters not exceeding those recommended by the supplier.
Temporary: the equipment may work for some time under conditions significantly exceeding the parameters recommended by the supplier, however, with long-term operation, environmental conditions can lead to equipment failure.
As follows from the last report of the mentioned group, the most efficient use of the equipment consists precisely in the well-planned alternation of all three modes of operation.
In this light, the research at the University of Missouri, on the effect of low air humidity on the occurrence of electrostatic discharges in server equipment, became very interesting. This circumstance at the moment is the main limiting parameter in case of extreme decrease of moisture in the circulating air. The study, as one would expect, showed a direct correlation between the increase in static charge in the "chains" with a decrease in the humidity level of the atmosphere, and the result was reversed with an increase in humidity. The study proved that the lower threshold of humidity in the server can be a value in the range of 8-25%. It is at this level of moisture that static electricity does not affect the operation of the equipment. The results of this study were also taken into account when ASHRAE engineers formulated their recommendations.
The relationship between temperature and humidity of atmospheric air is quite simple: the colder the air, the more dry it is. In turn, excessively dry air, as already mentioned, can cause an accumulation of static charge in electrical circuits and, as a result, can lead to the destruction of sensitive components. The latter circumstance brings an understanding that not only data centers constructed in desert regions, with a hot, dry climate, but also functioning at quite “comfortable” temperate latitudes, may face the problem of excessively dry air. In the winter period of the year, exploiting the IT infrastructure of the service, without taking into account all the risks of air drawn from the atmosphere, may receive abnormal situations threatening with the failure of network equipment.
At the same time, engineers in their published work consider the problem especially widely, for example, knowing such a negative feature of dry air as a static charge, they immediately suggest a set of measures to combat it. The main ally in this matter are materials that are not so susceptible to the accumulation of statics, as well as effective methods for its dispersion.
A well-functioning example, where the system for controlling air humidity is fully implemented, can be the recently built Facebook data centers in Oregon and North Carolina. By controlling the humidity in the server rooms, network engineers were able to reach an average PUE of less than 1.1.
“Watching at the moment a slight decline in the rate of progress in the hardware of the IT infrastructure, we are witnessing a more intensive growth in the“ breadth ”. Over the past 20 years, the world quickly transformed so much that sometimes simple solutions were missed, which can make the work of IT infrastructure components much more efficient, ”the report says, and also“ Instead of building strongholds all over the world ” opposing the world around us, we must use each specific location as efficiently as possible, and we must also effectively use the inexhaustible supply of energy contained in the atmosphere. Naturally, on a small scale, this kind of cooling system may not be too justified, but when it comes to giant data centers, over the years, the economic effect of these systems will amount to millions of dollars. ”
It is obvious that the climate of each particular locality imposes its own limitations on the possibility of using the air selected from the atmosphere as a free cooling medium. First of all, it should be borne in mind that it can not be used everywhere and secondly not always, moreover, the air masses throughout the planet are not very homogeneous, which is a particularly critical factor, besides the air temperature, naturally, its humidity.
')
The research group ASHRAE (abbreviation for the American Community of Engineers Heating and Cooling Ventilation Systems) has been working for many years on the study of the allowable range of air masses that can be used to cool equipment in data centers. A special subcommittee of this organization, which deals directly with the study of data centers, provided a report in which researchers came to an unambiguous conclusion. Increasing the temperature in the server room by just a few degrees, in comparison with the most commonly recommended range of 18-24 degrees, can significantly expand the geography and time periods for cooling data center equipment with atmospheric air, without additional mechanical manipulations with it. But the main condition, which by all means should have been met in the course of research, is that the savings on the data center energy costs should not expose the equipment to any risk, because its operating temperature range is very flexible.
But to what measure can this temperature be raised? Indeed, in the pursuit of profit, it is possible to jeopardize expensive equipment - say skeptics of the revision of standards. In this vein, the study of engineers at Google has become very interesting. Having in its assets a huge network infrastructure, for the company the issue of increasing temperatures was crucial for the effective conduct of its activities. First of all, researchers identified a “weak link” in the network bundle, which is most susceptible to failure. In this competition, with a serious margin, "hard drives" took the palm. They are the ones most exposed to high temperatures, in addition to this, they themselves are powerful generators of excess heat. After the subject was identified, various tests with whole batches of disks were used. Most of the tests showed that there is, of course, a connection between the temperature mode of the functioning of the disks and the occurrence of errors in their work, but not everything is as linear as it might seem.
According to the statistics presented, low operating temperatures (from 15 ° C to 30 ° C) can become no less dangerous for disks than the temperature regime of 45 ° C and higher.
In this context, we can recall the fact that data centers are not only network hardware, but also living people, without which all this equipment is nothing more than highly technological scrap metal. According to current sanitary norms (GOST 30494—2011), for example, the maximum allowable temperature in public, non-residential premises can reach 31 o C. By the way, this tolerance is also significantly higher than the recommended temperature range in server rooms.
The research group ASHRAE, during its existence, has already revised the recommended operating temperature range in the server room three times and each time the revision was in the direction of its increase. The chronology of these decisions 2004, 2008, 2011, apparently now is the time, without violating the time step, to wait again for another such decision. In addition to the temperature range, the humidity of the air circulating in the data center is an important factor. The relationship between moisture and air temperature is inseparable parameters. Although now there are already new data centers where these characteristics are put under tight control, for many previously built data centers this is a significant foundation for modernization.
According to the prepared specification from ASHRAE, there are three modes of equipment operation with different physical properties of air masses:
Recommended: environmental conditions that provide high performance and uninterrupted operation of equipment.
Valid: equipment operation mode is carried out with parameters not exceeding those recommended by the supplier.
Temporary: the equipment may work for some time under conditions significantly exceeding the parameters recommended by the supplier, however, with long-term operation, environmental conditions can lead to equipment failure.
As follows from the last report of the mentioned group, the most efficient use of the equipment consists precisely in the well-planned alternation of all three modes of operation.
Effect of low humidity on electrical circuits
In this light, the research at the University of Missouri, on the effect of low air humidity on the occurrence of electrostatic discharges in server equipment, became very interesting. This circumstance at the moment is the main limiting parameter in case of extreme decrease of moisture in the circulating air. The study, as one would expect, showed a direct correlation between the increase in static charge in the "chains" with a decrease in the humidity level of the atmosphere, and the result was reversed with an increase in humidity. The study proved that the lower threshold of humidity in the server can be a value in the range of 8-25%. It is at this level of moisture that static electricity does not affect the operation of the equipment. The results of this study were also taken into account when ASHRAE engineers formulated their recommendations.
Thermodynamics
The relationship between temperature and humidity of atmospheric air is quite simple: the colder the air, the more dry it is. In turn, excessively dry air, as already mentioned, can cause an accumulation of static charge in electrical circuits and, as a result, can lead to the destruction of sensitive components. The latter circumstance brings an understanding that not only data centers constructed in desert regions, with a hot, dry climate, but also functioning at quite “comfortable” temperate latitudes, may face the problem of excessively dry air. In the winter period of the year, exploiting the IT infrastructure of the service, without taking into account all the risks of air drawn from the atmosphere, may receive abnormal situations threatening with the failure of network equipment.
At the same time, engineers in their published work consider the problem especially widely, for example, knowing such a negative feature of dry air as a static charge, they immediately suggest a set of measures to combat it. The main ally in this matter are materials that are not so susceptible to the accumulation of statics, as well as effective methods for its dispersion.
A well-functioning example, where the system for controlling air humidity is fully implemented, can be the recently built Facebook data centers in Oregon and North Carolina. By controlling the humidity in the server rooms, network engineers were able to reach an average PUE of less than 1.1.
“Watching at the moment a slight decline in the rate of progress in the hardware of the IT infrastructure, we are witnessing a more intensive growth in the“ breadth ”. Over the past 20 years, the world quickly transformed so much that sometimes simple solutions were missed, which can make the work of IT infrastructure components much more efficient, ”the report says, and also“ Instead of building strongholds all over the world ” opposing the world around us, we must use each specific location as efficiently as possible, and we must also effectively use the inexhaustible supply of energy contained in the atmosphere. Naturally, on a small scale, this kind of cooling system may not be too justified, but when it comes to giant data centers, over the years, the economic effect of these systems will amount to millions of dollars. ”
Source: https://habr.com/ru/post/260103/
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