Abstract:
This relates to the manner in which computers are configured in a given area in order to conserve space and to deal with cooling issues associated with the close housing of a large number of computers. Efficient arrangements for efficiently increasing the density of computer configurations are shown, particularly when used in a network server or host environment.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation of U.S. patent appiication Ser. No. 10/279,153, filed Oct. 23, 2002, which is a continuation of U.S. patent application Ser. No. 09/479,824, filed Jan. 7, 2000, now U.S. Pat. No. 6,496,366, which claims priority to Provisional Patent Appiication Serial No. 60/161,578, filed Oct. 26, 1999, the disclosures of which are incorporated by reference herein in their entirety. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This relates to the manner in which computers are configured and provided in a given area in order to conserve space and deal with cooling issues associated with housing a large number of computers. Aspects of the invention assist with increasing the density at which computers may be provided, particularly in a network server or host environment.  
         BACKGROUND OF THE INVENTION  
         [0003]    Many computers today are assembled from components built to one or more industry standards. The use of standardized components using specific interfaces allows for ease of supply, efficiency in production, and competitiveness in pricing. A further advantage associated with the use of standardized computer components, as opposed to custom pieces, is that of performance.  
           [0004]    The dollar-for-dollar performance advantage of many standardized components over similar custom components can be viewed as a beneficial consequence of the balance between the resources invested in each product and the efforts to optimize its function. Standardized components have higher sales volume and return potential than custom components, thereby generally allowing additional resources to be invested in their production. Standardized components also face broader competition regarding performance. Therefore, if sales are to be made at a given price point, the performance of the corresponding standardized component must excel.  
           [0005]    In contrast, even when custom components are desired, it is often not economically feasible to optimize performance. The paramount concern is to meet the specific needs calling for the customization. This is particularly so when space conservation is the primary consideration. Although the number of smaller computers available for duty where space conservation is important has increased, they are typically very expensive. Also, these smaller custom computer systems often suffer in the areas of computing speed and system reliability relative to computers using less costly standardized components.  
           [0006]    It should be noted, however, that additional factors affect the performance of existing space-saving computer systems. The compaction of layout in shrinking main board sizes results in component crowding and imparts additional design constraints which hinder design for optimal performance. Crowding can adversely affect the manner in which components are connected as well as result in significant heat dissipation problems. Further compromises are often made in shrinking computer sizes. To conserve space, smaller fans or fewer fans may be included in a design. Also, custom-made power supplies and data drives may be required in producing a compact system. As with main boards designed for small size, these units often lag in performance relative to their standardized counterparts.  
           [0007]    The use of custom components introduces further difficulties when they break down. Supply issues can be such a difficulty as to make it more feasible to replace an entire machine so as not to lose its computing power for an extended time, rather than wait for repair components necessary to get the existing machine up and running. This difficulty is often compounded by an increased failure rate experienced with custom components.  
           [0008]    All of these disadvantages aside, there exists a need for compact computer systems in the server industry. It is this very need which has justified acceptance of current compact systems despite their performance and thermodynamic disadvantages. Especially with the advent and rise of the Internet and World Wide Web, an increasing demand for more computers to be connected to serve as network hosts or servers has arisen.  
           [0009]    The function of network serves may be carried out by more traditional “servers” in the form of powerful computers usually configured to perform specific functions. Another more recently developed model in providing network services is with grouped computers or “modules” linked, in part, through software such as the VNC software package available through Oracle, Inc., to form a “farm” or “puzzle” of computers working together. Computers set up in a farm or otherwise provided in a coordinated set will include their own processors, data drives and so-forth in order that each may accomplish a fraction of the work intended for the whole.  
           [0010]    Farms, in particular, have several advantages over typical servers. One advantage is the combined speed of processors working together in a coordinated manner. Another advantage resides in the redundancy of a farm&#39;s structure. If any one module fails, it can be extracted or replaced with no ill effect other than the fractional loss of the farm&#39;s capacity. Put another way, failure of part the set of computers does not shut down the whole. In contrast, when any portion of a server fails, the whole system may go down. If the failure itself does not cause the loss, shutting down the computer for a necessary repair certainly will.  
           [0011]    Irrespective of the type of network host that might be employed, it is clear that there is a growing need for compact, serviceable network resources. This has lead to an increasing need for space in which to house the network host units and a consolidation of spaces where they are located. Sites known as co-location sites where numerous networked computers find a home now exist. Space for the computers is typically rented at such sites. Rent calculations may be based on the overall space occupied, power consumption and bandwidth handled by the computers occupying the space. Because of the relationship between such factors, it will often be in favor of both a co-location site and computer service provider to maximize both the density and performance efficiency of the computers at a given site. By increasing the density at which computers may be packed into a given area, the service provider benefits since less space is required for a given number of computers; the co-location site benefits since the ultimate bandwidth available in association with the space available may be greatly increased.  
           [0012]    Other less apparent benefits stem from conserving the space a host computer occupies. In many instances, it will be economically feasible to forestall the retirement of otherwise outdated host computers since the cost of the space they occupy is relatively lower, thereby justifying their continued service for a period of time. On the other hand, where it is preferred to only maintain the highest-end computers in service, the savings available by minimizing the size of such computers without hindering performance is quite clear. There exists a need for computer systems adapted for realizing these many advantages.  
           [0013]    Typically, at a site where numerous computers are connected to a network, the computers are provided stacked in racks arranged in repeating rows or cells. Access to the computers is necessary for servicing, upgrading hardware, loading software, attaching cables, switching power on and off, and so forth. The elimination of as much access space as is feasible can increase the density of computer systems that may be provided for a given square footage of area at a site. Moveable rack solutions can be used to decrease access space requirements. However, they have not gained wide acceptance. Consequently, there exists a need to eliminate extraneous access space while still maintaining the use of relatively inexpensive, standard (or more-or-less standard) racks.  
           [0014]    A rack that is currently being widely used measures roughly 19 inches wide, 30 inches deep and 74 inches high. In at least one co-location site, these racks are lined up in rows of roughly 10-30 units with access doors on each side of a rack. Access aisles are provided on both sides of the rows. Many of the racks are filled with cumbersome computers mounted on sliders which are attached through mounting holes provided in the front and back of the rack. Regardless of the chassis design of the computers (or lack thereof where computers are merely built on open trays with their components uncovered) and how they are mounted to the racks, data devices included in the computer are accessed from the front. Main board I/O&#39;s, other I/O&#39;s, power cords and such items are typically accessed from the back. It is this latter design aspect which not only results in inefficiency in the amount of access space required, but also in the frequent inefficiencies associated with having to administer services to both sides of a computer. Consequently, there exists a need for computers useable in a network setting that are accessible and fully serviceable from a single side.  
           [0015]    In order to significantly increase the density at which computers in a given space are provided, the only solution to date has been to shrink the computer&#39;s box. As such, there exists a need to increase the density at which computers may be provided in a given space by what means are possible while still having the ability to utilize standardized components. Aspects of the present invention including single-sided access help in this regard.  
           [0016]    Additionally, there exists a need for improved cooling of computers, especially where large numbers are provided. This need is compounded by increased computer density. Features of the invention help meet this need as well. In certain situations, this need to maintain acceptable computer temperatures can compete with the need to maintain the environment in which the computers are housed at an acceptable temperature without exorbitant expenditures for environmental cooling. Certain features of the invention directed at cooling the computers help in this regard.  
         SUMMARY OF THE INVENTION  
         [0017]    A system designed to maximize the density of computers that may be provided in a given space is provided. Several features of the system may enable one to provide a higher density of computer systems at a site. Preferably, the computers are built from standardized or readily-available components, except for the chassis herein described.  
           [0018]    One way in which embodiments of the present invention conserves space and increases computer density is to eliminate the need for access to both the front and back of a computer. This is accomplished by an inventive chassis design in which ports for items requiring physical access are placed only at the front of the chassis. Items requiring physical access include, but are not limited to: various data drives or storage devices and physical input and output sockets. Preferably, the rear of a computer chassis made according to the invention is free of any such access ports. However, this “front access” feature of the present invention does not require that each and every physical attachment to a computer be located in front of the machine. Desirably, those which require physical access periodically or would significantly hinder forward removal of the machine from a rack in which it may be stacked are provided for at the front of the chassis. At least those features located on the main board which would normally be accessed from behind and accessible data drives are provided for in the front of the inventive chassis.  
           [0019]    The above-described chassis configuration allows for effective placement of computer components in a back-to-back arrangement within a rack or other supporting structure. This back-to-back placement of computer components within a rack forms a highly desirable aspect of the invention. Such placement often doubles or further multiplies the density potential for rack computer systems, e.g., those in which the computers would otherwise be mounted one unit deep. The back-to-back mounting of computer chassis may also involve the back-to-back placement of full-function computers linked to one another or the back-to-back placement of a computer and a device such as a drive array serving the computer which it abuts.  
           [0020]    Another aspect of the invention which aids in increasing the density at which computers may be provided is attained by placing the inventive chassis in a back-to-back fashion in a manner so that a space between the backs of the various chassis is present when the units are in a rack. Cooled or forced air may then be provided in this rectangular back space (and, if so desired, to the space between the sides of the chassis and side panels of some racks) to pass through a computer chassis and be vented through the front of the machine. Optimally, this back-to-front flow of cooling gas traveling through the computer is directed to particularly hot-running or temperature-sensitive components such as power supplies or CPU&#39;s. Various inlets, vents, fans, and baffles may be specially-configured or controlled to provide desired flow properties and optimize cooling and/or temperature stabilization. Ideally, forced air at ambient temperature or forced and/or cooled air as low as about 40° F. (5° C.) or lower is used. Air provided in the space between computers and or the rack which house them may come either from above through ductwork typically present in a building or below where advantage may be taken of the fact that heat rises.  
           [0021]    The backspace and optional sidespace between the computers or rack sides may be used in another advantageous manner. Especially where maintaining a lower environmental temperature is a concern, a flow reversed from that described above will be advantageous. Such reversed flow may be accomplished by drawing ambient air by fans and/or a partial vacuum through the computer chassis past heat-generating components and venting it from the common space between the computers by a hood or plenum, vent or other means. Common ductwork may take the heated air out of the site. Alternately, it may be preferred that each hood independently exhausts air out of the site in which the computers are located. Providing front-to-back flow will cool computer components as well as help maintain lower ambient temperatures than possible with other high-density network computer solutions. As desired above, it is preferred that the flow of cooling gas is directed to or by hot-running or temperature sensitive components.  
           [0022]    Providing cooling flow in either a back-to-front direction or a front-to-back direction as possible with the hardware and/or configuration of computers and racks as disclosed herein forms part of the present invention. Generally, this invention includes methods and also various hardware components either in isolation or in combination where they may work together to ultimately achieve the desired results.  
           [0023]    In accordance with embodiments of the present invention, a set of computers is provided. The set comprises: at least two computers, each computer comprising at least one heat-generating component, each computer adapted to permit air to flow in the computer such that airflow goes through, over, or adjacent to the at least one heat-generating component to cool the at least one heat-generating component; and a rack configured for the at least two computers to be placed in a back-to-back configuration such that the rack and computers will cooperate to direct air that flows through the computers (1) up to exit the rack through an upper section of the rack, (2) down to exit the rack through a lower section of the rack, or (3) both.  
           [0024]    In accordance with embodiments of the present invention, a method of cooling one or more heat-generating components in two or more computers is provided, where such computers are mounted back-to-back in a rack. The method comprises: directing air into and through each of the computers to cool at least one heat-generating component; and directing the air (1) up to exit the rack through an upper section of the rack, (2) down to exit the rack through a lower section of the rack, or (3) both. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]    Each of the following figures diagrammatically illustrates aspects of the present invention. The illustrations provide examples of the invention described herein. It is contemplated that combinations of aspects of specific variations or combinations of the specific variations themselves are within the scope of this disclosure.  
         [0026]    [0026]FIG. 1 shows a configuration of the inventive chassis as it may be built-up with certain components to form a computer.  
         [0027]    [0027]FIGS. 2A, 2B,  2 C,  2 D and  2 E show configurations of the inventive chassis.  
         [0028]    [0028]FIGS. 3A and 3B show back-to-back computer system configurations.  
         [0029]    [0029]FIG. 4 shows an oblique view of a rack partially filled with computers according to the invention.  
         [0030]    [0030]FIGS. 5 and 6 show partial cut-away side views of racks filled with computers according to the invention. 
     
    
     DETAILED DESCRIPTION  
       [0031]    [0031]FIG. 1 shows a configuration of the inventive chassis as it may be assembled with standard components. Although the use of standard components is preferred, of course, none of the components must be so. The chassis  2  will usually include a chassis body  4  and a chassis cover  6 . A main board compartment  8 , and a power supply compartment  10  separated by a baffle  12  are optionally provided. Preferably, the main board compartment  8  is sized to fit an ATX form factor main board  14 . Preferred main boards include models N44BX, L44GX, 810, 810E and C440GX by Intel, Inc. Such main boards typically include an I/O shield  16 . The chassis  2 , is preferably made of zinc plated mild steel sheet metal, with the front panel  18  painted. Rivets, welds or other suitable fastening methods may be used to secure various components and hold the chassis body  4  in shape.  
         [0032]    The main board compartment  8  is preferably of a height sufficient to include room for a 3.5 inch disk drive  20  above main board  14  in a port  22  in the front panel  18  of the front section  24  of the chassis. The variation shown in FIG. 1 is “2U” in height. Especially when using different CPU configurations, alternate heights as described below may be advantageous.  
         [0033]    Whatever the configuration, a port  26  for the main board shield  16  will be provided in the front panel  18  of the chassis body  4 . A port  28  in the front panel for an external SCSI drive (not shown) or other such device may also be provided. Another port  30  of such a size to fit numerous connectors (such as a parallel port connector) or a port for an Ethernet card (not shown) to fit in the main board  14  is also provided in the variation shown in FIG. 1. Further, ports  34  for switches are optionally provided.  
         [0034]    The front panel  18  defining the various ports may be configured to attach to a rack by providing interface sections  36  extending from the sides  38 ,  40  of the chassis body  4 . In-line with the power supply compartment  10 , in the variation of FIG. 1, the front panel  18  also includes a port  42  capable of receiving a 5¼ inch device  44 . A number of devices may be optionally used in this port. As diagrammatically pictured, a drive  44 , such as a removable-medium drive (e.g., CD, DVD, ZIP, JAZZ, DAT, Smart Cards, Flash disk and Tape drives or others whether designed for a standard size desktop or network computer or of smaller size for a portable computer or the like) may variously be used in a hard-wired, hot-swappable or replaceable configuration. A hot-swappable hard drive or CD ROM may be preferred.  
         [0035]    Common to all such drives is the need for access for the purpose of changing the data storage media or for pulling the device itself. The same is true for the connectors attachable to the shield  16  of the main board  14  discussed above and/or for connectors to accommodate USB/external SCSI or parallel port devices or other auxiliary data drives configured for plug-in use. In the variation shown in FIG. 1, optional port  46  accommodating a power cord fitting to a power supply  48  to be housed in the power supply compartment  10  is provided.  
         [0036]    Preferably, the chassis  2  is configured so power cords such as those which would be connected at port  46  will be located at one side of the unit, while other cords, wires or the like for data transmission will be connected at the other side. In this way, two well-organized columns of connection members will be developed when a rack is filled with chassis  2  spanning the front of it.  
         [0037]    Preferably, the power supply  48  for use in the assembled computer is made of high-quality standard components. In the configuration shown in FIG. 1, a customized power supply shield  50  may be provided with a step  142  from a lower region  52  to an upper region  54  in order to accept the larger 5¼ inch devices. Just as the power supply shield  50  may include a step  142  to provide clearance for desirable drives in the power supply compartment  10 , the baffle  12  may include a step or jog  140 . The jog  140  shown is provided as clearance for both the 5¼ inch port  42  and for certain desirable main boards  14  in the main board compartment  8  while maintaining a total frontal width narrow enough to fit in a typical rack having a 19 inch wide opening.  
         [0038]    A hard drive  56  may be placed below any 5¼ inch device used. It is also possible to provide various brackets elsewhere within the chassis body  4  to mount additional hard drives as space permits. The placement of the hard drive  56  indicated is, however, optimal in view of the cooling features provided in this variant of the invention. While vents  58 ,  60  and  62  and fans  76  in front of the vents are provided foremost to generate a stream of air optionally in a direction as indicated to cool the power supply  48 , the drive  56  is exposed to a beneficial stream of cooling air as well. Vents  64  and  66  in the power supply cover  50  allow the air to move through the same without significant impediment.  
         [0039]    In a manner similar to that of the configuration of the power supply compartment  10  which is intended to pass cooling gas or air across the power supply, vents  68 ,  70  and  72  and fans  76  in front of the vents provided in the main board compartment  8  direct cooling air over or near the CPU(s)  74  of the main board  14 . In the variant pictured, a diagonal flow of air may be achieved as indicated.  
         [0040]    The cooling of the chassis compartments  8  and  10  may be provided by fans  76  which severally run continuously while the computer is on or alternatively there may be more selective control of at least some of the fans  76 . For instance, where a thermal control unit  78  is included in the computer design, separate channels of the unit may be set to monitor the temperature of the chambers and turn on and off fans in each of the chassis compartment or the device itself to help maintain temperatures as constant as possible. Such a set-up can reduce thermal cycling issues that may arise due to differing power consumption and waste-heat generation of components (especially CPUs) depending on their usage. Also, the direction of air flow may be varied by switching the direction in which the fans  76  turn.  
         [0041]    [0041]FIG. 2A shows the variation of the inventive chassis which is shown built-up in FIG. 1, as may any of the other chassis pictured and/or described. The chassis of FIGS. 2B , 2C,  2 D and  2 E include ports with generally identical functions as indicated by corresponding sizing, profile and/or numbering. The differences between the chassis are a matter of what ports are considered to be preferred for the computer configuration desired. All configurations, however, exhibit the common feature that each of their ports for all components requiring or designed for intermittent access by a user are on one side of the chassis. In the variant shown in FIG. 2C, no jog in the baffle  12  is required since no 5¼ inch device port is provided.  
         [0042]    In the variant shown in FIG. 2D, no baffle is included at all. To account for the loss of such support as provided by a baffle  12  in the other variants of the invention, a top flange  132  is preferably provided around the entire periphery of the chassis body  4 . Further, as shown in FIG. 2D, the chassis body  4  need not include any ports for internal data drives. As alluded to above, it is possible to use the chassis in combination with external data devices configured for intermittent connection. Dedicated ports in the face  18  may be provided for such accessibility. Alternately, optional ports  144  provided for a main board I/O&#39;s ports may suffice.  
         [0043]    [0043]FIGS. 2D and 2F show a “1U” variant of the inventive chassis. Such a configuration may be used to efficiently house a 810X main board. The stacking of 1U chassis in a rack enables the provision of up to four times the number of computers as compared to others (such as Rack-Mount 02 systems available through Silicon Graphics, Inc.) that may be provided in a given rack. Therefore, up to 84 IU computers may be housed in a 74 inch high standard rack.  
         [0044]    A 1U chassis will be particularly advantageous to use where additional CPU power is desired for a farm or set of computers in a rack since use of such a slim chassis will result in packing more processor power into less space in a rack. However, fewer peripherals may be used in such a slim design. Also, presently, typical two CPU main boards may not be used in a 1U chassis. In view of such limitations in assembling a rack of computers, it will often be advantageous to employ computers built in chassis of varying heights. Still as long as a sufficient number of 1U chassis are employed in combination with taller units, it is possible to provide racks with upwards of 40 or 60 computers for a 74 inch high rack.  
         [0045]    By virtue of each chassis being configured to accept a main board  14  in a horizontal orientation and the remaining layout of the chassis adapted to accept other components beside the same (whether on the opposite side of a baffle wall  12  or not), it is possible to maintain the low profiles displayed such as with 1U and 2U designs specifically described. This configuration is also useful for producing low profile computers of heights anywhere between about 1U and about 3U.  
         [0046]    The approximate height of a 1U chassis is about 1¾  1   3 / 4  inches. Naturally, the various 2U, 3U, 4U and taller models have heights corresponding to multiples of the 1U height. As clearly known in the art, a 1U chassis unit is mountable between three mounting holes on a standard rack. Taller units span an increasing number of holes.  
         [0047]    As with the other chassis in FIGS.  2 A- 2 C, the variations shown in FIG. 2D may be mounted on the rack by its front flange members at interface section  36 . Due to the height of the chassis, the number or width of vents  80  and  84  may be increased as shown to maximize the open cross-sectional area for cooling gas to pass through a chassis. Additional, but smaller, fans may also be employed. Also, it may be advantageous to use smaller data drives in such a chassis, e.g. drives made for laptop or portable computers, or to eliminate provision for internal drives and rely only on ports for external drives as described above.  
         [0048]    Especially with the unmodified flange-mount chassis designs shown in FIGS.  2 A- 2 D, where longer chassis are desired for use in a back-to-back configuration in a standard rack, it will be preferred to mount the computers to racks using longer bolts (or other affixation means) and with spacers  112  between the interface section  36  and opposing rack portions  114  across from each on a rack as indicated in FIG. 4. As pictured in FIG. 2D, integrated bolts  134  of a style pressed in to the chassis body  4  so they will remain with the unit and serve as handles to remove the chassis may be generally preferable with any chasis for affixing the chassis  2  to the rack  98  along each side  114 . Spacer  112  may be the height of only a single chassis, of the rack mounting portions  114  or somewhere in between. In this way, it will be possible to produce longer chassis and still maintain the advantageous backspace  106  as otherwise possible such as described below.  
         [0049]    The goal of providing longer chassis for use with a standard rack can be accomplished with the inventive chassis in other manners. As shown in FIG. 2E, brackets  116  attachable to the chassis itself that may be set back or offset from the face  18  of the unit in order to provide a chassis position which is pushed forward from the norm. Here brackets  116  are provided with holes  118  with which to mount the chassis to the rack sides  114 . Depending on the depth of offset  120  of each bracket  116 , or how far back the brackets  116  are located on the chassis body  4 , it is possible to advance the front of the chassis a significant amount out the front of the rack so as to be able to provide a lengthy chassis which may still be mounted back-to-back with other chassis (of similar or different configuration) as described herein.  
         [0050]    Yet another manner to accomplish the same goal is to provide an integral flange or interface section  36  configured like that of the bracket  116  so it provides an area for attachment set back from the face  18  of the chassis. Such an interface section  36  will provide the desired forward offset  120  to enable back-to-back placement of longer chassis than otherwise possible in a standard rack without the use of spacers  112  or the like.  
         [0051]    Another advantageous feature that may be utilized in the present invention to include a face plate  122  for use with the chassis. Such a face plate  122  as shown in FIG. 2E may be used with any variation of the invention. The face plate  122  will typically include ventilation holes  124  to allow cooling air or other gas to pass through. In a preferred variation, the ventilation holes span most of the face of the piece. Optimally, the face plate  122  is connected to the chassis by a hinged interface. However, any slip fit, friction fit or snap fit to the front of the chassis will suffice. At least one side of the face plate will be left open so that cables, wires and like connected to the front of a computer assembled according to the present invention can be routed out the open area(s) to connect to such components as required for the computer to serve in a network. Preferably, both sides are open to accommodate the dual wire/cable column configuration for power and data cables, respectively, as discussed above.  
         [0052]    While any of the variations of the chassis described herein may make use of the face plate  122 , only higher-end models will use a separate bezel  126 . In this variation of the invention (and in like variations of differing height vent configuration, baffle configuration, etc.), the bezel  126 , once connected, forms part of the chassis body  4 . In the variation shown, one or more common fasteners attach each bracket  116  and the bezel  126  to the sides  128  of the chassis body  4 .  
         [0053]    An advantage of using such a bezel  126  is that it may be customized easily or exchanged for another which is more advantageous for a given computer to be built. In essence, the bezel  126  allows for increased design and marketing flexibility since changes in chassis  2  configuration can be made in a piecemeal fashion. This differs from those variations of the chassis which include an integrally-produced front panel  18 .  
         [0054]    Regardless of such variations as possible, a preferred commonality between all the configurations of the chassis  2  is the general placement of vents. While some differences are shown between the chassis shown in FIGS.  2 A- 2 E, at least one set of vents  80  is provided in the rear section  82  of the chassis body  4  and another set  84  in the front section  24 . Depending on the placement and selection of components with which to build a computer in the inventive chassis  2 , the placement of the vents in the rear on the back panel  86  or side panels  38  or  40  may be varied. However, for those aspects of the invention in which venting and the flow of air through the chassis is relevant, some vents will be provided in the front  18  of the chassis  2 . Even when not used with other aspects of the present invention, the air flow may travel from the rear section  82  to the front section  24 . Alternately, it may travel in the other direction. In fact, direction of air flow may be set depending on the desired effect on the environment and/or condition(s) of the environment. It may even be switchable to account for changing environmental conditions such as variations in the temperature of the site housing the computers due to seasonal climate or the difference in environmental temperatures between day and night or other events.  
         [0055]    The advantageous use of air flow through the entire chassis and across heat-generating components is still possible where only one compartment is provided within the chassis  2 . While the baffle  12  is often advantageous for isolating compartments for placement of hot-running components and aiding the vents in directing air flow, its use is merely optional. Especially in instances where a removable power supply is provided in a port such as port  42  in the front of the chassis, the advantages of a two-compartment chassis design wanes.  
         [0056]    [0056]FIG. 3A shows an example of an arrangement in which use of a removable, power supply would be particularly advantageous. In this variation of the invention, a computer module  88  is built in accordance with that shown and described in FIG. 3B utilizing a chassis with front access for components, except a redundant two-socket power module (not shown) is provided. Placed at the back of unit  88  is an “array” or “RAID” module  90  including a number of data drives  44 . Together the modules  88  and  90  form a powerful system  92  optimized for space and accessibility.  
         [0057]    In such a configuration, the computer module  88  need not include a hard drive. In the array module  90 , any number or type of drive(s), including those discussed above may be provided in either hard-wired or swappable configurations. Drives which require accessibility when the modules  88  and  90  are mounted back-to-back are accommodated by ports in the array  90  chassis on the outwardly-facing side. In this specialized variation of the invention, a port for a connector  94 , such as a SCSI interface, is provided in the rear of each unit  88  and  90 . Optimally, connector ports  136  and  138  will be at the bottom of each piece so units of differing height may still interface with one another.  
         [0058]    A more typical application of the inventive chassis is shown in FIG. 3B. Here, full computers  96  built with the chassis  2  are provided in a back-to-back configuration. Preferably they are hooked up in the manner of a farm. Generally, no connections will run between the units as with the computer system  92  discussed above. This is, however, possible. It will be advantageous particularly where power is shared over an interface  94  between computers  96  in FIG. 3A. This enables swapping out a removable power supply such as that which may be provided in port  42  while maintaining power to each computer  96 .  
         [0059]    It is preferred that back-to-back pairs of computers  96  (whether connected or not) are mounted in a standard rack  98  in one layer after another as shown in FIG. 4. They may be mounted to the rack on slides (not shown), by integral interface sections  36  brackets  116  as alternately described above or otherwise. When no slide is used, it is preferred to place strips of adhesive TEFLON tape  100  or the like on the surface of at least one computer under or above another. While the chassis  2  are sufficiently strong and the assembled units light enough to be self-supporting when bolted into a rack, the tape  100  takes up space to provide support and makes sliding a unit out from a rack for service more convenient.  
         [0060]    The rack shown in FIG. 4 will hold up to  40  computers  96  built with the 2U inventive chassis. As alluded to above, this is because the use of the chassis in a back-to-back configuration permits the doubling of the number of computers that may be stored in a standard rack. Of course, when utilizing chassis according to the present invention of different heights, this ratio changes. To do this, (unless using spacers  112  or offset mounting brackets  116  or interface portions  36 ), regardless of the height of the chassis  2  the depth of the chassis  102  must be less than half the available depth  104  of the rack in order to stack computers two deep. Without the use of specialized mounting configurations, preferably the chassis depth  102  is less than 15 inches (38 cm) when configured for a 30 inch (76 cm) deep rack.  
         [0061]    In a most preferred variation of the invention, the depth of the chassis  2  is even less. For use in a standard 30 inch deep rack, the chassis depth  102  is 13.5 to 14.5 inches deep (34 to 37 cm). This is so because when a sufficient number of computers are placed back-to-back in a rack as contemplated in the present invention, an advantageous optional back space  106  between about 1 to 6 inches, preferably about 1 to 3 inches is formed behind the computers. When side panels  108  are provided on the rack  98 , the back space  106  is complemented by side space  110  between the sides of the computers  38 ,  40  and the rack side panels  108  to form an H-shaped space. The space behind the computers may, however, be cordoned off to leave only a rectangular volume if desired.  
         [0062]    When back-connected units such as array modules  90  and computer modules  88  or  96  are used in combination in a rack  108 , they are also preferably configured in this manner to define (preferably with other computers, of one height or another, as described in the present invention) such channels or spaces. The back-to-back connection between the units will not significantly hinder the functionality provided by the air space. However, it is highly undesirable to have the air space cluttered by other structure such as cables, cords and the like. This is why the front-access configurations of the inventive chassis are advantageously used in conjunction with providing an air space between computer modules within a rack  98  or other enclosure as might be used.  
         [0063]    As mentioned above, the space provided between computer modules may be advantageously used in a number of ways. For instance, as illustrated in FIG. 5 a positive airflow as optionally indicated from above, below or in both directions, may be provided to the space. Providing a measure of gas pressure will tend to force air through vents  80  in the units defining the space as indicated. If enough pressure is provided, it would be possible, in principle, to provide computers without fans.  
         [0064]    However, the primary intent in providing air under pressure to the back space  106  and/or side space  110  is to assist the fans or to provide a measure of redundancy so that if one or more fans fail that the air pressure maintains some level of flow within the computer chassis. Such a backup can provide a technician the time cushion needed before a system overheats (in order to take the computer off-line or out of the network or farm for repairs) before vital componentry is burnt up.  
         [0065]    Even where forced air is not provided, the air mass may be cooled. By drawing cooled air through the individual computers past hot-running components, improved cooling will result. Most preferably, however, forced and cooled air, such as standard air conditioning (HVAC) is provided with a compounding of benefits resulting.  
         [0066]    Another benefit of providing a controlled flow of air in the back space  106  and/or side space  110  to pass through the computers and be vented out the front as indicated in FIG. 5 is the opportunity to provide filtered air to the air intakes of the computers. This will control the accumulation of harmful dust in the machines. Additionally, lower power consumption costs may result for a site housing many computers utilizing the cooling features of the invention. Efficient application of cooled air to power-intensive components is possible with the advantages of this aspect of the present invention.  
         [0067]    It is noted that the cooling features of the present invention discussed above should do still more than save energy and space to benefit the bottom line for the parties making use of them. It should also provide welcome relief for those who work at a co-location site that has fully-adopted the new form factor offered by the present invention since it will not be necessary to keep the entire environment at frigid levels in order to keep the computers present within running acceptably.  
         [0068]    Sometimes, however, it will be preferable to reverse the airflow from the back-to-front airflow as variously shown in FIG. 5 to front-to-back airflow as variously shown in FIG. 6. As such, air travels from the environment, through the front of the computers, into the backspace  106  and/or sidespace  110  and out of the rack  98 . A vent in the form of a hood enclosure or plenum  130  optionally including fan(s)  146  may be provided to exhaust air heated by components within the computer to the exterior of the site at which the computers are located via ductwork or independently. Irrespective of its structure, in this variation of the invention, the vent  130  may be passive or utilize a partial vacuum generated by a fan or by some other means. Preferably, the air is exhausted from inside the rack  98  in an upward direction to take advantage of the buoyancy exhibited by heated air. It is, however, possible to vent the air from below or from above and below simultaneously.  
         [0069]    When higher velocities of air are reached within the channel formed between the components placed back-to-back within the rack  98 , a venture effect will increasingly assist in drawing air through the machines from the environment in which they are housed. This effect may be best accomplished by top and bottom venting of the rack.  
         [0070]    Reasons for providing sets of computers utilizing front-to-back airflow into and out of the common space  106  and/or  110  include, but are not limited to, maintaining an acceptable overall temperature of the environment in which the computers are housed, controlling environmental cooling or air-conditioning costs and providing a self-contained unit that may be individually vented so as to avoid contribution to an overall heating problem of a facility or exacerbating heating problems of nearby, less-robust systems by blowing hot air in their direction. To aid in providing a discrete system which will not contribute to overall heating problems at a site, further isolation of the system may be accomplished by providing insulation at, along or within the sides of the rack  98  and/or at any optional door(s) provided.  
         [0071]    As similarly possible with the present invention when set up for back-to-front cooling flow, with front-to-back cooling flow the effect of loss of fan(s) in a computer may be minimized. Provision of partial vacuum within backspace  106  and/or sidespace  110  will insure a continued draw of air into a computer if fans fail, thereby providing a measure of redundancy; it will also generally assist the fans in providing air flow through the chassis  2  when everything is working properly.  
         [0072]    Regardless of which flow direction is chosen (or if there is switching between the flow directions), advantageous flow across heat-generating components which must be cooled is possible with the present invention. Generating directional flow of cooling gas through the computer chassis from one side to another according to the present invention avoids recirculation or cavitation of already heated air that hinders cooling as typically occurs with other computers  
         [0073]    Further details as to the use or other aspects of the system described herein may be drawn from the background that is intended to form part of the present invention. It is noted that this invention has been described and specific examples or variations of the invention have been portrayed. The use of those specific examples is not intended to limit the invention in any way. Additionally, to the extent that there are variations of the invention which are within the spirit of the disclosure and are equivalent to features found in the claims, it is the intent that the claims cover those variations as well. All equivalents are considered to be within the scope of the claimed invention, even those which may not have been set forth herein merely for the sake of relative brevity. Also, the various aspects of the invention described herein, in any manner, may be modified and/or used in combination with such other aspects also described to be part of the invention either explicitly, implicitly or inherently in order to form variations considered to be part of the invention.