Patent Publication Number: US-11395433-B2

Title: Server system

Description:
This application is a continuation of U.S. patent application Ser. No. 15/058,103, filed Mar. 1, 2016, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     Organizations such as on-line retailers, Internet service providers, search providers, financial institutions, universities, and other computing-intensive organizations often conduct computer operations from large scale computing facilities. Such computing facilities house and accommodate a large amount of server, network, and computer equipment to process, store, and exchange data as needed to carry out an organization&#39;s operations. Typically, a computer room of a computing facility includes many server racks. Each server rack, in turn, includes many servers and associated computer equipment. 
     Computer systems typically include a number of components, such components include printed circuit boards, mass storage devices, power supplies, and processors. Some known computer systems include a plurality of large, multiple-processor computers that are configured into rack-mounted components, and then are subsequently positioned within a rack system. Some known rack systems include 40 such rack-mounted components and such rack systems will therefore generate as much as 10 kilowatts of waste heat. Moreover, some known data centers include a plurality of such rack systems. 
     Some computer systems are rack mounted servers that include a number of hard disk drives (for example, eight or more hard disk drives) to provide adequate data storage. Typically, the hard disk drives for servers are of a standard, off-the-shelf type. Standard, off-the-shelf hard disk drives are often a cost effective solution for storage needs because such hard disk drives can be obtained at relatively low cost. Nonetheless, in server designs using such standard hard disk drives, the arrangement of the hard disk drives may leave a substantial amount of wasted space in a server chassis. This wasted space, especially when multiplied over many servers in a rack, may result in inadequate computing or storage capacity for a system. 
     Some servers that include a number of hard disk drives use a centralized controller to control accesses to the hard disk drives, such as reads and writes. In such server designs using a centralized controller, a failure of the controller or ancillary equipment associated with the controller, may cause all the hard disk drives of the server to be unreachable. Thus reducing the reliability of the server. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating a rack comprising multiple server systems, according to some embodiments. 
         FIG. 2A  is a top view of an interior of a server system, according to some embodiments. 
         FIG. 2B  is a front view of an interior of a server system, according to some embodiments. 
         FIG. 2C  is a top view of a portion of a backplane of a server system, according to some embodiments. 
         FIG. 3  is a perspective view illustrating a rack comprising multiple server systems, according to some embodiments. 
         FIG. 4A  is a top view of an interior of a server system, according to some embodiments. 
         FIG. 4B  is a front view of an interior of a server system, according to some embodiments. 
         FIG. 4C  is a front view of a backplane of a server system, according to some embodiments. 
         FIG. 5  illustrates a server device that occupies up to an equivalent volume of space as a mass storage device, according to some embodiments. 
         FIG. 6  illustrates installing mass storage devices and a server device in a server system, according to some embodiments. 
         FIG. 7  illustrates removing a server device from a server system while a portion of the server system is in operation, according to some embodiments. 
     
    
    
     While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims. As used throughout this application, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words “include,” “including,” and “includes” mean including, but not limited to. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Various embodiments of computer systems, and systems and methods for performing computing operations, are disclosed. According to one embodiment, a system for storing data includes a rack and a server system coupled to the rack. The server system includes a chassis and an array of devices mounted within the chassis of the server system. The array of devices includes mass storage devices, such as hard disk drives, mounted in the array. The mass storage devices are coupled to a backplane of the array. In addition, the array includes a server device mounted in the array and coupled to the backplane of the array, wherein the server device occupies up to an equivalent volume of space in the chassis as one of the mass storage devices in the array. The server device is configured to control storage operations for the mass storage devices in the array and comprises a network port for other systems to access data stored on the mass storage devices over a network. In some embodiments, an array may include multiple backplanes communicatively coupled with each other. For example, a server system may include an array that includes hard disk drives and a server device that controls access to the hard disk drives. The server device may be mounted in the array along with the hard disk drives and occupy up to an equivalent volume of space in the chassis of the server system as one of the hard disk drives. One or more backplanes may communicatively couple the hard disk drives of the array with the server device of the array. 
     According to one embodiment, a server system includes a chassis and an array of devices mounted in the chassis, wherein the array includes mass storage devices and a server device. The server device is communicatively coupled to the mass storage devices of the array and is configured to control storage operations of the mass storage devices in the array. The server system also includes one or more additional arrays of devices mounted in the chassis. Each of the additional arrays includes mass storage devices mounted in the additional arrays and respective server devices mounted in each respective additional array. The respective server devices are communicatively coupled to the mass storage devices of the respective arrays and are configured to control storage operations of the mass storage devices of the respective arrays. In some embodiments, each of the arrays and additional arrays may form a separate logical node within the server system. 
     According to one embodiment, a method includes coupling mass storage devices in respective slots of an array of slots in a chassis of a server system, coupling a server device in a particular slot of the array of slots in the chassis of the server system, wherein the particular slot of the array occupies up to an equivalent volume of space in the chassis as other ones of the slots of the array in which the mass storage devices are coupled, wherein the server device is configured to control storage operations for the mass storage devices in the array of slots and comprises a network port for communicating with other systems. 
     As used herein, “backplane” means a plate or board to which other electronic components, such as mass storage devices, server devices, etc. can be mounted. In some embodiments, mass storage devices, which can include one or more hard disk drives, are plugged into a backplane in a generally perpendicular orientation relative to the face of the backplane. In some embodiments, a server device is plugged into a backplane in a generally perpendicular orientation relative to the face of the backplane. In some embodiments, a backplane includes one or more power buses that can transmit power to components on the backplane, and one or more data buses that can transmit data to and from components installed on the backplane. 
     As used herein, a “cable” includes any cable, conduit, or line that carries one or more conductors and that is flexible over at least a portion of its length. A cable may include a connector portion, such as a plug, at one or more of its ends. 
     As used herein, “circuit board” means any board or plate that has one or more electrical conductors transmitting power, data, or signals from components on or coupled to the circuit board to other components on the board or to external components. In certain embodiments, a circuit board is an epoxy glass board with one or more conductive layers therein. A circuit board may, however, be made of any suitable combination of materials. 
     As used herein, “chassis” means a structure or element that supports another element or to which other elements can be mounted. A chassis may have any shape or construction, including a frame, a sheet, a plate, a box, a channel, or a combination thereof. In one embodiment, a chassis is made from one or more sheet metal parts. A chassis for a computer system may support circuit board assemblies, power supply units, data storage devices, fans, cables, and other components of the computer system. 
     As used herein, “computing” includes any operations that can be performed by a computer, such as computation, data storage, data retrieval, or communications. 
     As used herein, “data center” includes any facility or portion of a facility in which computer operations are carried out. A data center may include servers dedicated to specific functions or serving multiple functions. Examples of computer operations include information processing, communications, testing, simulations, power distribution and control, and operational control. 
     As used herein, “mounting” a particular element on another element refers to positioning the particular element to be in physical contact with the other element, such that the other element provides one or more of structural support, positioning, structural load transfer, stabilization, shock absorption, some combination thereof, or the like with regard to the particular element. The mounted particular element may be positioned to rest upon one or more upper surfaces of the other element, independent of coupling the elements via one or more coupling elements. In some embodiments, mounting the particular element to another element includes coupling the elements such that the other element provides one or more of structural support, positioning, structural load transfer, stabilization, shock absorption, some combination thereof, or the like with regard to the particular element. 
     As used herein, a “rack” means a rack, container, frame, or other element or combination of elements that can contain or physically support one or more computer systems. In some embodiments a rack is a standard 19″ rack that conforms to EIA standards. 
     Some servers that mount in a rack may be general purpose servers, while some rack-mounted servers may be specially designed for storage capacity. Such specially designed servers may include storage servers that include several hard disk drives and controller servers that include controllers that manage storage operations directed at the hard disk drives in the storage servers. A controller server may be mounted in a separate chassis in a separate rack slot from a rack slot in which a storage server is mounted. In such servers, some available space in the slot of the rack in which the controller server is mounted may go unutilized, thus reducing the number and density of hard disk drives that can be mounted in the rack. For example, only a portion of a space of a rack slot in which a controller server is mounted may be occupied by components of the controller server or only a portion of an interior space within a chassis of a controller server may be occupied by components of the controller server. Also, some servers that include a separate controller server may be configured such that the controller server and hard disk drives controlled by the controller server form a single logical node. In such servers, if a common component fails, such as a component in the controller server, the whole logical node including all of the hard disk drives controlled by the controller server may become inaccessible. Thus in such designs a large number of hard disk drives may be rendered unavailable due to a single component failure. 
     In some embodiments, wasted space in a separate controller server may be eliminated by including a server device in a same chassis of a server system along with mass storage devices, such as hard disk drives, that are controlled by the server device. Also, failure impact due to a single component failure may be reduced by including several logical nodes, each with their own server device, in the same chassis of the server system. In some embodiments, a server system may include a server device mounted in a same chassis with mass storage devices, such as hard disk drives. The server device may occupy an equivalent volume of space in the chassis as one of the mass storage devices. Thus a greater density of mass storage devices per rack may be achieved by eliminating unutilized space of a separate controller server as described above. Also, in some embodiments, multiple logical nodes each comprising its own server device and an array of mass storage device controlled by the server device may be included in a chassis of a server system. The multiple logical nodes may be independent of each other, so that if a component in one logical node fails, such as a server device of the logical node, the other logical nodes in the server system may not be affected by the failure and continue to be available to perform storage operations. 
     A chassis of a server system may be a single enclosure that is configured to mount in a rack. For example, mass storage devices and server devices mounted in a chassis of a server system may be installed in a rack as a single whole system or device that occupies a slot in the rack. In some embodiments, a height of a server system may span multiple 1 Us in a standard 19″ EAI rack. For example, a server system may have a height of 1 U, 2 U, 3 U, 4 U, 5 U, 1.5 U, 2.5 U, etc. 
       FIG. 1  is a perspective view illustrating a rack comprising multiple server systems, according to some embodiments. System  100  includes rack  102  and server systems  104 ,  106 , and  108  mounted in rack  102 . Each of server systems  104 ,  106 , and  108  include multiple arrays of device slots with mass storage devices and a server device mounted in respective device slot of respective ones of the arrays. Each array of mass storage devices and a respective server device forms a separate logical node of multiple logical nodes of the server systems. For example, server system  104  includes 9 logical nodes  110 , wherein each logical node includes an array of mass storage devices and a server device for controlling storage operations directed at the array of mass storage devices. In some embodiments, each logical node of a server system includes mass storage devices and a server device mounted in device slots of a sled, wherein the sled is configured to move into and out of a chassis of the server system independently of other components of the server system, such as other sleds comprising other logical nodes.  FIG. 1  illustrates sled  112  partially extended out of chassis  114  of server system  104 . Mass storage devices  116  and server device  118  are mounted in device slots of an array of device slots of sled  112 . Each of logical nodes  110  may include a separate array of device slots with mass storage devices and a server device mounted in the array of device slots as shown in sled  112 . In some embodiments, a server device, such as server device  118 , occupies up to an equivalent volume of space within chassis  114  as one of the mass storage devices of the server system, such as one of mass storage devices  116 . In some embodiments, a server device, such as server device  118 , may have a form factor that is equivalent to a form factor of a mass storage device, such as one of mass storage devices  116 . In some embodiments, a server device, such as server device  118 , may have a form factor that is smaller than a form factor of a mass storage device, such as one of mass storage devices  116 . For example, server device  118  may have a form factor such that server device  118  can fit within a space that has a volume equivalent to a volume of a mass storage device, such as one of mass storage devices  116 . 
     A server device, such as server device  118 , may include one or more network ports and be configured to communicate with systems outside of server system  100 . For example, server device  118  may be configured to receive read and write requests from other computing systems and/or servers to read data from and write data to mass storage devices  116 . 
     In some embodiments, an array of devices in a server system that forms its own logical node, such as one of logical nodes  110  in server system  104 , may include more than one server device in the logical node. For example, a logical node, such as one of logical nodes  110 , may include multiple server devices in the same array of devices that forms the logical node. The multiple server devices of a logical node may be configured to coordinate with each other to control storage operations related to mass storage devices of the logical node, such as mass storage devices  116 . In some embodiments, a ratio of server devices to mass storage devices may be adjusted by adding or removing mass storage devices and/or server devices from an array of devices that forms the logical node. 
     In some embodiments, server devices of a logical node may perform compute operations in addition to managing storage operations related to an array of mass storage devices of the logical node. In some embodiments, multiple server devices may be included in a single logical node to provide additional computing capacity for the logical node. 
     In some embodiments, mass storage devices and/or a server device of a logical node are configured to be removed from the logical node while other logical nodes of the server system are in operation. For example, a mass storage device has been removed from a device slot of sled  112 . In some embodiments, mass storage devices of a logical node may be hot pluggable, such that a mass storage device can be removed from a logical node while other mass storage devices of the logical node remain available to perform storage operations and the server device of the logical node remains in operation. For example, mass storage devices  116  and server device  118  of sled  112  may perform storage operations while sled  112  is partially removed from server system  104  and while a mass storage device is removed from one of the device slots of sled  112 . Also, in some embodiments, a server device, such as server device  118  may be removed from a device slot of a server system, while other logical nodes, such as other ones of logical nodes  110  remain in operation. For example, server device  118  may be removed from a device slot of sled  112  while other ones of logical nodes  110  of server system  104  remain in operation. 
     In some embodiments, data storage operations for mass storage devices of a logical node, such as one of logical nodes  110 , may be controlled by a server device included in the logical node in an array of devices slots of the logical node along with a mass storage devices of the logical node mounted in the array of device slots without using an additional controller. The mass storage devices of a logical node may be controlled without an external controller controlling storage operations of the mass storage devices of the logical node. For example each of logical nodes  110  may include their own server device and not rely on an external controller mounted in another rack slot in rack  102  to control data operations of mass storage devices in respective ones of logical nodes  110 . 
     By including server devices in an array with mass storage devices in a single chassis, a high density of mass storage devices in a rack can be achieved. For example, in some embodiments, a 48 U standard 19″ rack may include over 1,440 3.5″ hard disk drives along with server devices for controlling the hard disk drives, wherein the hard disk drives are mounted in device slots of multiple arrays included in multiple server systems mounted in the rack and wherein each array includes a server device mounted in a device slot of the respective array. In some embodiments, a 48 U standard 19″ rack may include more or less hard disk drives mounted in device slots of multiple arrays. In some embodiments, other rack sizes may be used. 
     In some embodiments, a server system may include arrays of device slots that run from a front side of the server system to a back side of the server system. For example,  FIGS. 2A-2C  illustrate an embodiment of a server system with multiple arrays of device slots with mass storage devices and respective server devices mounted in the respective arrays, wherein the arrays run from a front side of the server system to a back side of the server system. 
       FIG. 2A  is a top view of an interior of a server system, according to some embodiments. Server system  200  includes chassis  202 , mass storage devices  204  and server devices  205 . Mass storage devices  204  and server devices  205  are mounted in device slots of arrays  206 ,  208 ,  210 ,  212 ,  214 ,  216 ,  218 ,  220 , and  222 . Each of arrays  206 ,  208 ,  210 ,  212 ,  214 ,  216 ,  218 ,  220 , and  222  includes its own server device  205  and forms a separate logical node of server system  200 . In some embodiments, each of arrays  206 ,  208 ,  210 ,  212 ,  214 ,  216 ,  218 ,  220 , and  222  include a separate sled that is configured to move into and out of chassis  202  independently from one another. In some embodiments, a server system, such as server system  200 , may include 9 arrays of device slots with 16 device slots in each array. In some embodiments, a server system, such as server system  200  may have a height of 4 U or 5 U. In some embodiments, a server system may have different heights and may include more or less device slots in a chassis or more or less arrays. 
     In some embodiments, a backplane may communicatively couple mass storage devices of a logical node with a server device of the logical node. In some embodiments, cables may be used to communicatively couple mass storage devices of a logical node with a respective server device of the logical node without using a backplane. In some embodiments, both a backplane and cables may be used to communicatively couple mass storage devices of a logical node with a respective server device of the logical node. 
       FIG. 2B  is a front view of an interior of a server system, according to some embodiments.  FIG. 2B  illustrates backplanes  224  mounted beneath mass storage devices  204  and server devices  205  of arrays  206 ,  208 ,  210 ,  212 ,  214 ,  216 ,  218 ,  220 , and  222  in a space between chassis  202  and mass storage devices  204  and server devices  205 . 
     In some embodiments, mass storage devices and a respective server device of an array of a server system may be coupled together via a backplane. In some embodiments, a backplane of an array may be mounted beneath mass storage devices and a server device of the array in a space between a bottom of the chassis and the bottom of the mass storage devices and server device. In some embodiments, a backplane may transmit data between components coupled to the backplane, such as mass storage devices and a server device. A backplane may include a data connection that couples with a server device, such as one of server devices  205 . In some embodiments a server device, such as one of server devices  205  may be connected to a backplane via a connector that is similar to a connector used to connect mass storage devices to the backplane and in some embodiments, a separate data connection may be used to couple a backplane with a storage server via a cable. In some embodiments a connector used to connect mass storage devices to a backplane may be configured to accept both mass storage devices and server devices such that mass storage device and server devices can be interchangeably coupled to a backplane via the same connector. In some embodiments a connector for coupling a mass storage device and/or a connector for coupling a server device to a backplane may comprise one or more keys or other particular configurations that prevent server devices and mass storage devices from being interchangeably coupled to the same connector. 
       FIG. 2C  is a top view of a portion of a backplane of a server system, according to some embodiments. Backplane  224  may be the same backplane  224  illustrated in  FIG. 2B . Backplane  224  includes connectors  226  mounted on circuit board  228 . In some embodiments, ones of connectors  226  may be configured to only couple with mass storage devices or may be configured to only couple with server devices. In other embodiments, ones of connectors  226  may be configured to interchangeably couple with mass storage devices and server devices, such as mass storage devices  204  and server devices  205 . Backplane  224  also includes power connection  230  and data connection  232 . Power connection  230  may be configured to couple to a power source that provides power to server system  200  and data connection  232  may couple with a server device, such as one of server devices  205 . A server device, such as server device  205 , may in turn be coupled to a larger network such as a rack level network, data center network, or other network. For example, data operations from clients of a server system  200  may be directed at server devices  205  of server system  200  and data received and provided by server system  200  may be received from or provided to clients of server system  200  via server devices  205  and data connections  232 . In some embodiments, a backplane may include a data connection configured to couple the backplane to a larger network such as a rack level network, data center network, or other network. In some embodiments, power may be distributed from power connection  230  via circuit board  228  to components coupled to backplane  224  such as mass storage devices  204  and a server device  205 . In some embodiments, a server system, such as server system  200  may not include a backplane  224  and may include cables to distribute power to mass storage devices  204  and a server device  205 . In some embodiments, cables may transmit data between mass storage devices  204 , a server device  205 , and clients of the server system. In some embodiments both cables and a backplane may be used to distribute power and transmit data within a server system  200 . 
     In some embodiments, components of a server system, such as server system  200 , may be cooled by air moving devices such as fans. For example in some embodiments, fans may be mounted in space  234  in chassis  202  of server system  200  to direct air to flow over mass storage devices  204  and server devices  205 . In some embodiments, a server system, such as server system  200 , may be liquid cooled. For example, server system  200  may include pipes, tubes, or other suitable means to convey a liquid coolant to mass storage devices  204  and server devices  205  to remove waste heat from mass storage devices  204  and server devices  205 . In some embodiments, a server system, such as server system  200 , may be cooled by an external cooling system, such as a rack level cooling system. In some embodiments, other suitable means may be used to remove waste heat from mass storage devices and server devices of a server system. 
     The arrangement of mass storage devices and server devices illustrated in  FIGS. 1-2  is an example of a server system with mass storage devices and server devices mounted in arrays in a common chassis. However, in some embodiments, mass storage devices and server devices may be arranged in other arrangements in a server system. For example, in some embodiments, mass storage devices and respective server devices may be arranged in arrays that span a width of a server system, for example from a left side of the server system to a right side of the server system when the server system is mounted in a rack. For example,  FIG. 3  is a perspective view illustrating a rack comprising multiple server systems, according to some embodiments. System  300  includes rack  302  and server systems  304 ,  306 , and  308 . Server system  304  includes chassis  316 , mass storage devices  314 , server device  310 , and backplane(s)  312 . Mass storage devices  314  and server device  310  are mounted in an array of device slots in chassis  316  that spans a width of rack  302 , e.g. from a left side of rack  302  to a right side of rack  302 . Rack  302  is illustrated with ellipses between server system  306  and server system  308  to indicate that a rack, such as rack  302 , may include more or less server systems. In some embodiments, rack  302  may be a 48 U rack and each server system may have a height that occupies 3 Us of rack  302 . In some embodiments, a server system may have different heights. For ease of illustration, server system  304  is shown partially removed from rack  302 . In some embodiments, a server system, such as server system  304 , may include multiple arrays of mass storage devices and respective server devices that span a width of the server system. For example, in some embodiments, server system  304  may include 6 arrays of server systems. Also, for ease of illustration, only server system  304  is shown partially removed from rack  302 . However, in some embodiments, server systems  306  and  308  may include similar components in a similar arrangement as shown for server system  304 . 
       FIGS. 4A-C  illustrate different views of a server system with arrays of mass storage devices and server devices arranged in horizontal arrays, according to some embodiments. Any of server systems  304 ,  306 , and  308  may include similar components in a similar arrangement as illustrated in  FIGS. 4A-C . 
       FIG. 4A  is a top view of an interior of a server system, such as one of server systems  304 ,  306 , or  308 , according to some embodiments. Server system  400  includes mass storage device  402 , server devices  404 , and backplanes  406 . In server system  400 , groups of mass storage devices  402 , respective ones of server devices  404  and respective backplanes  406  are organized in multiple arrays that each form a logical node within server system  400 . For example server system  400  includes arrays  408 ,  410 ,  412 ,  414 ,  416 , and  418 . Each of arrays  408 ,  410 ,  412 ,  414 ,  416 , and  418  includes a group of mass storage devices  402  and a respective server device  404  that coordinates data storage operations of the mass storage devices  402  in the respective array. Because each array it its own logical node, a failure of a component, such as a server device in one array does not prevent other arrays or logical nodes within server system  400  from continuing to perform storage operations. 
     In  FIG. 4A , a backplane  406  is illustrated as being coupled to each one of arrays  408 ,  410 ,  412 ,  414 ,  416 , and  418 . In some embodiments, a single back plane may be coupled to multiple arrays. For example, a backplane may be mounted between successive arrays in a chassis of a server system and mass storage devices and server devices may be coupled to two sides of the backplane. For example a backplane between arrays  416  and  418  may be coupled to mass storage devices  402  and server device  404  of array  418  on a first side of the backplane and may be coupled to mass storage devices  402  and server device  404  of array  416  on a second side of the backplane. In some embodiments, mass storage devices and server devices of respective arrays may be coupled together via cables without using a backplane. In some embodiments, both cables and backplanes may be used to couple together mass storage devices and server devices. For example, server device  404  may include multiple ports, a first port may be coupled via a cable to a first backplane that is coupled with a portion of mass storage devices  402  in array  418  and server device  404  may be coupled via another cable to another backplane that is coupled to another portion of mass storage devices  402  in array  418 . In some embodiments, other suitable means may be used to couple mass storage devices with a server device that coordinates storage operations associated with the mass storage devices. 
       FIG. 4B  is a front view of an interior of a server system, according to some embodiments.  FIG. 4B  illustrates a front view of an interior of server system  400  and backplane  406  coupled to mass storage devices  402  and server device  404 . As shown in  FIG. 4B , in some embodiments multiple backplanes  406  may be coupled to mass storage devices and a server device.  FIG. 4C  is a front view of a backplane of a server system, according to some embodiments.  FIG. 4C  illustrates one of backplanes  406 . A backplane may include multiple connectors, such as connectors  422 . A backplane may also include power connectors, such as power connector  424 , and data connectors, such as data connectors  426 . In some embodiments, a server system may be connected to a larger network via a server device, such as one of server devices  404 . The server device may in turn be connected to mass storage devices, such as mass storage devices  402  via cables connected to data connectors  426 . In some embodiments, connectors of a backplane, such as connectors  422  may couple to mass storage devices and one of the connectors may couple with a server device, such as server device  404 . In some embodiments, a server device, such as server device  404 , may be coupled to a backplane, such as backplane  406  via a cable connector, such as one of data connectors  426 . Another data connector of a backplane, such as another one of data connectors  426 , may couple the backplane with an additional backplane. 
     In some embodiments, components of a server system, such as server system  400 , may be cooled by air moving devices such as fans. For example in some embodiments, fans may be mounted in or couple with chassis  420  of server system  400  to direct air to flow over mass storage devices  402  and server devices  404 . In some embodiments, a server system, such as server system  400 , may be liquid cooled. For example, server system  400  may include pipes, tubes, or other suitable means to convey a liquid coolant to mass storage devices  402  and server devices  404  to remove waste heat from mass storage devices  402  and server devices  404 . In some embodiments, a server system, such as server system  400 , may be cooled by an external cooling system, such as a rack level cooling system. In some embodiments, other suitable means may be used to remove waste heat from mass storage devices and server devices of a server system. 
       FIG. 5  illustrates a server device that occupies an equivalent volume of space as a mass storage device, according to some embodiments. Server device  500  illustrated in  FIG. 5  may be any of the server devices described in  FIGS. 1-4 . In some embodiments, server device  500  may have a form factor that occupies up to an equivalent volume of space as a mass storage device, such as a 3.5″ hard disk drive. 
     Server device  500  includes system on a chip  502 , memory devices  510 , power connector  508 , network interface controller  504 , network port  506 , management and control circuit  512 , boot drive  514 , and connectors  516  and  518 . System on a chip  502  comprises a processor and interface for communicating with mass storage devices via connectors  516  and  518 . System on a chip  502  also comprises a communication interface with memory  510 . In some embodiments system on a chip  502  may be an SoC, a general purpose processor, an application specific integrated circuit (ASIC), or another device that provides processing capability and communicates with connectors  516  and  518 . In some embodiments, management and control circuit  512  manages conditions of server device  500  such as temperature conditions. In some embodiments, management and control circuit  512  includes an interface for connecting with an external heath monitoring system, such as an intelligent platform management interface (IPMI). In some embodiments, memory devices  510  are RAM devices such as double data rate fourth generation synchronous dynamic random-access memory (DDR4) or other suitable RAM devices. In some embodiments, network port  506  is a small form factor pluggable 10 gigabit port or other suitable port for network connection. In some embodiments, power connector  508  may be configured to receive electrical power via a cable connection, and in some embodiments, power connector  508  may be configured to couple with a backplane and receive electrical power via the backplane. In some embodiments, boot drive  514  is a solid state drive that stores program instructions for booting server device  500 . In some embodiments, boot instructions for server device  500  may be stored in a remote location and boot drive  514  may be omitted. In some embodiments connectors  516  and  518  are mini SAS HD connectors. In some embodiments connectors  516  may include two mini SAS HD connectors with four lanes each and connectors  518  may include two mini SAS HD connectors with four lanes each. Thus connectors  516  and  518  may collectively include 16 lanes for connecting with 16 mass storage devices. In some embodiments, other suitable connectors may be used for connectors  516  and  518 . In some embodiments, communication via connectors  516  and  518  may be in accordance with a FibreChannel standard, Serial ATA standard, or other suitable standard. In some embodiments, a backplane may couple with connectors  516  and  518  to directly couple server device  500  with mass storage devices via a backplane without using expanders or host bus adapters to connect server device  500  to mass storage devices. 
     In some embodiments, a server device, such as server device  500  may be mounted in a device slot of an array of device slots with connectors  516  and  518  oriented down towards a bottom of the device slot and coupled with a backplane that runs beneath mass storage devices of the array and the server device mounted in the device slot. In some embodiments, a server device, such as server device  500  may be mounted in a device slot with connectors  516  and  518  oriented parallel to the device slot. A backplane may be positioned between successive arrays of mass storage devices and server devices so that connectors  516  and  518  couple with the backplane that is positioned between successive arrays of mass storage devices and server devices. In some embodiments, a server device, such as server device  500  may be coupled to backplanes via cables connected to connectors  516  and  518 . 
     In some embodiments, a server device such as server device  500  may be integrated into a backplane. For example the respective components of server device  500  described above may be mounted on a circuit board of a backplane. In some embodiments, a server device, such as server device  500  may be liquid cooled. 
     In some embodiments, a server device, such as server device  500 , may have a form factor that is equivalent to a form factor of a standard 3.5″ hard disk drive. In some embodiments a server device, such as server device  500 , may have a different form factor. 
       FIG. 6  illustrates installing mass storage devices and a server device in a server system, according to some embodiments. At  602  mass storage devices are coupled in respective device slots of an array of device slots within a chassis of a server system. In some embodiments, a server system may include multiple arrays of device slots within the chassis of the server system. In some embodiments, device slots may be included in a sled of a server system and coupling mass storage devices in respective device slots of a server system may include coupling the mass storage devices into device slots of the sled of the server system. 
     At  604  a server device is coupled in a device slot of the array of device slots. In some embodiments a server system chassis may include multiple arrays of devices slots and a separate server device may be coupled in a device slot of each array. In some embodiments each array that includes mass storage devices and a respective server device may form its own logical node within the server system. 
     At  606 , the mass storage devices of the array are communicatively coupled with the server device of the array. In some embodiments each array may include its own server device communicatively coupled with mass storage devices of the array. In some embodiments a server device and mass storage devices may be communicatively coupled via a backplane. In some embodiments, cables may communicatively couple a server device with mass storage devices of an array. In some embodiments, multiple backplanes and cables may be used to communicatively couple a server device with mass storage devices. In some embodiments, an array may include 16 device slots, with one of the device slots occupied by a server device and the remaining 15 device slots occupied by mass storage devices. In some embodiments, a server system may include 6, 9, or some other number of arrays of device slots in a common chassis. In some embodiments, mass storage devices of the array and a server device of the array may be communicatively coupled when the mass storage devices and the data server device are coupled in respective slots in the array. For example,  606  may be performed as part of performing  602  and  604 . 
     As discussed at  604  and  606 , in some embodiments, a server system may include multiple arrays of device slots. At  608  additional mass storage devices and additional server devices are coupled in device slots of additional arrays of device slots within a server system. 
     At  610 , the server system is coupled in one or more slots of a rack. In some embodiments, a server system may occupy 3 U, 4 U, or 5 U of rack space in a rack. In some embodiments a server system may have different heights. In some embodiments, multiple server systems may be mounted in a rack. 
       FIG. 7  illustrates removing a server device from a server system while a portion of the server system is in operation, according to some embodiments. At  702 , a sled of a server system is at least partially removed from a chassis of the server system. In some embodiments, a server system may include multiple logical nodes in a common chassis. Each sled of a server system may comprise its own logical node, so that partially removing a sled from a server system does not affect storage operations of other logical nodes mounted in other sleds within the chassis of the server system. In some embodiments, other logical nodes may continue to perform storage operations while a particular sled comprising a particular logical node of mass storage devices and an associated server device are at least partially removed from a chassis of a server system. 
     At  704 , a server device is removed from the sled that has been partially slid out of the chassis of the server system. In some circumstances, a mass storage device may be removed from the sled instead of the server device. In some embodiments, mass storage devices of a server system may be hot pluggable such that a mass storage device can be removed from and added to an array of device slots while remaining mass storage devices communicatively coupled with a server device associated with the array (or sled) may continue to perform data storage operations. 
     At  706 , a different server device or the same server device is installed in the device slot from which the server device was removed. In some circumstances, it may be desirable to replace or repair a server device, for example due to a failure associated with the server device. In some embodiments, an additional server device may be installed in another slot of the sled. For example, additional compute capacity may be desired for the logical node that corresponds with the particular sled that is partially removed. In some embodiments, device slots of a sled may be configured to accept both mass storage devices and server devices, such that a mass storage device can be removed from a sled, such as the sled that is partially removed, and replaced with a server device to increase a computing capacity of a logical node corresponding to the sled. 
     At  708 , the sled is re-inserted into the chassis of the server system. At  710  data storage operations are performed in relation to the mass storage devices mounted in the device slots of the sled using the new or returned server device. 
     In some embodiments, mass storage devices in a server system are standard, off-the-shelf hard disk drives. Examples of suitable hard disk drive form factors may include 3.5″, 5.25″, and 2.5″. In one embodiment, a standard 3.5″ hard disk drive is installed in a device slot of a plurality of device slots of an array along with other standard 3.5″ hard disk drives. In some embodiments, a server device of an array may have a form factor equivalent to a 2.5″, 3″, 3.5″, or 5.25″ hard disk drive. 
     Although in the embodiments described above, some of the server systems have been described as being 3 U, 4 U, or 5 U in height, server systems may in various embodiments be 2 U, 4 U, 5 U, 6 U or any other height or dimensions. 
     The various methods as illustrated in the figures and described herein represent example embodiments of methods. The order of method may be changed, and various elements may be added, reordered, combined, omitted, modified, etc. 
     Although the embodiments above have been described in considerable detail, numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.