Modern computer architecture may be viewed as having three distinct subsystems which when combined, form what most think of when they hear the term computer. These subsystems are: 1) a processing complex; 2) an interface between the processing complex and I/O controllers or devices; and 3) the I/O (i.e., input/ouput) controllers or devices themselves.
A processing complex may be as simple as a single microprocessor, such as a Pentium microprocessor, coupled to memory. Or, it might be as complex as two or more processors which share memory.
The interface between the processing complex and I/O is commonly known as the chipset. On the north side of the chipset (i.e., between the processing complex and the chipset) is a bus referred to as the HOST bus. The HOST bus is usually a proprietary bus designed to interface to memory, to one or more microprocessors within the processing complex, and to the chipset. On the south side of the chipset are a number of buses which connect the chipset to I/O devices. Examples of such buses include: ISA, EISA, PCI, PCI-X, and AGP.
I/O devices are devices that allow data to be transferred to or from the processing complex through the chipset, on one or more of the busses supported by the chipset. Examples of I/O devices include: graphics cards coupled to a computer display; disk controllers (which are coupled to hard disk drives or other data storage systems); network controllers (to interface to networks such as Ethernet); USB and Firewire controllers which interface to a variety of devices from digital cameras to external data storage to digital music systems, etc.; and PS/2 controllers for interfacing to keyboards/mice. The I/O devices are designed to connect to the chipset via one of its supported interface buses. For example, modern computers typically couple graphic cards to the chipset via an AGP bus. Ethernet cards, SATA, Fiber Channel, and SCSI (data storage) cards, USB and Firewire controllers all connect to a PCI bus, and PS/2 devices connect to an ISA bus.
One skilled in the art will appreciate that the above description is general. What should be appreciated however, is that regardless of the type of computer, it will include a processing complex for executing instructions, an interface to I/O, and I/O devices to allow the processing complex to communicate with the world outside of itself. This is true whether the computer is an inexpensive desktop in a home, a high-end workstation used for graphics and video editing, or a clustered server which provides database support to hundreds within a large organization.
A problem that has been recognized by the present inventors is that the requirement to place a processing complex, interface and I/O within every computer is costly, and lacks modularity. That is, once a computer is purchased, all of the subsystems are static from the standpoint of the user. The ability to change a processing complex while still utilizing the interface and I/O is extremely difficult. The interface or chipset is typically so tied to the processing complex that swapping one without the other doesn't make sense. And, the I/O is typically integrated within the computer, at least for servers and business desktops, such that upgrade or modification of the I/O is either impossible or cost prohibitive.
An example of the above limitations is considered helpful. A popular network server designed by Dell Computer Corporation is the Dell PowerEdge 1750. This server includes a microprocessor designed by Intel (a Xeon processor), along with memory (e.g., the processing complex). It has a server class chipset for interfacing the processing complex to I/O (e.g., the interface). And, it has onboard graphics for connecting to a display, onboard PS/2 for connecting a mouse/keyboard, onboard RAID control for connecting to data storage, onboard network interface controllers for connecting to 10/100 and 1 gig Ethernet; and a PCI bus for adding other I/O such as SCSI or Fiber Channel controllers. It is believed that none of the onboard features are upgradeable.
So, as mentioned above, one of the problems with this architecture is that if another I/O demand emerges, it is difficult, or cost prohibitive to implement the upgrade. For example, 10 gigabit Ethernet is on the horizon. How can this be easily added to this server? Well, perhaps a 10 gig Ethernet controller could be purchased and inserted onto the PCI bus. Consider a technology infrastructure that included tens or hundreds of these servers. To move to a faster network architecture requires an upgrade to each of the existing servers. This is an extremely cost prohibitive scenario, which is why it is very difficult to upgrade existing network infrastructures.
This one-to-one correspondence between the processing complex, the interface, and the I/O is also costly to the manufacturer. That is, in the example above, much of the I/O is manufactured on the motherboard of the server. To include the I/O on the motherboard is costly to the manufacturer, and ultimately to the end user. If the end user utilizes all of the I/O provided, then s/he is happy. But, if the end user does not wish to utilize the onboard RAID, or the 10/100 Ethernet, then s/he is still required to pay for its inclusion. This is not optimal.
Consider another emerging platform, the blade server. A blade server is essentially a processing complex, an interface, and I/O together on a relatively small printed circuit board that has a backplane connector. The blade is made to be inserted with other blades into a chassis that has a form factor similar to a rack server today. The benefit is that many blades can be located in the same rack space previously required by just one or two rack servers. While blades have seen market growth in some areas, where processing density is a real issue, they have yet to gain significant market share, for many reasons. One of the reasons is cost. That is, blade servers still must provide all of the features of a pedestal or rack server, including a processing complex, an interface to I/O, and I/O. Further, the blade servers must integrate all necessary I/O because they do not have an external bus which would allow them to add other I/O on to them. So, each blade must include such I/O as Ethernet (10/100, and/or 1 gig), and data storage control (SCSI, Fiber Channel, etc.).
One recent development to try and allow multiple processing complexes to separate themselves from I/O devices was introduced by Intel and other vendors. It is called Infiniband. Infiniband is a high-speed serial interconnect designed to provide for multiple, out of the box interconnects. However, it is a switched, channel-based architecture that is not part of the load-store architecture of the processing complex. That is, it uses message passing where the processing complex communicates with a Host-Channel-Adapter (HCA) which then communicates with all downstream devices, such as I/O devices. It is the HCA that handles all the transport to the Infiniband fabric rather than the processing complex. That is, the only device that is within the load/store domain of the processing complex is the HCA. What this means is that you have to leave the processing complex domain to get to your I/O devices. This jump out of processing complex domain (the load/store domain) is one of the things that contributed to Infinibands failure as a solution to shared I/O. According to one industry analyst referring to Infiniband, “[i]t was overbilled, overhyped to be the nirvana for everything server, everything I/O, the solution to every problem you can imagine in the data center . . . but turned out to be more complex and expensive to deploy . . . because it required installing a new cabling system and significant investments in yet another switched high speed serial interconnect”.
Thus, the inventors have recognized that separation between the processing complex and its interface, and I/O, should occur, but the separation must not impact either existing operating systems, software, or existing hardware or hardware infrastructures. By breaking apart the processing complex from the I/O, more cost effective and flexible solutions can be introduced.
Further, the inventors have recognized that the solution must not be a channel based architecture, performed outside of the box. Rather, the solution should use a load-store architecture, where the processing complex sends data directly to (or at least architecturally directly) or receives data directly from an I/O device (such as a network controller, or data storage controller) without message passing. This allows the separation to be accomplished without affecting a network infrastructure or disrupting the operating system.
Therefore, what is needed is an apparatus and method which separates the processing complex and its interface to I/O from the I/O devices.
Further, what is needed is an apparatus and method which allows processing complexes and their interfaces to be designed, manufactured, and sold, without requiring I/O to be included within them.
Additionally, what is needed is an apparatus and method which allows a single I/O device to be shared by multiple processing complexes.
In addition, what is needed is an I/O device that can be shared by two or more processing complexes using a common load-store fabric.
Further, what is needed is an apparatus and method that allows multiple processing complexes to share one or more I/O devices through a common load-store fabric.
Additionally, what is needed is an apparatus and method that provides switching between multiple processing complexes and shared I/O.
Further, what is needed is an apparatus and method that allows multiple processing complexes, each operating independently, and having their own operating system domain, to view shared I/O devices as if the I/O devices were dedicated to them.
And, what is needed is an apparatus and method which allows shared I/O devices to be utilized by different processing complexes without requiring modification to the processing complexes existing operating systems or other software.