Modular 1U System (Patent Pending) General Description The Little Dragon system is a system of components that may be combined together in various ways to create a series of systems with capabilities that would normally require several different designs. The basic concept of the case is a tube, designed for rack or other mountings, that is combined with different end-caps that enable differing functionalities. A series of motherboards have been custom designed specifically to work as part of the Little Dragon system along with various standard motherboards. The special motherboards provide specialized capabilities that give the Little Dragon systems a series of capabilities beyond those of any known 1U system. This is a working document that is subject to frequent change as decisions are made to add or modify the definitions given herein. John Matlock Itox, Inc. Version 2.0a, 11-29-00
Overview www.itox.com.1u/design/ In designing a conventional computer case design the process begins with decisions as to what the case will hold. The form factor or style of the motherboard and the size and number of disk drives and expansion cards to be accommodated generally defined the exterior dimensions and to a certain extent the overall shape. Because of this custom, the traditional way a rack mount case was designed was much the same. The external size was fixed by the rack size, but the overall layout, length, and placement of components tended to follow the design practices of conventional computer cases. In the Little Dragon system of 1U rack mount systems, the exterior dimensions of the case are fixed and the design proceeds in reverse. The tight dimensions make the overall design of the case more a problem of fitting in what is possible rather than first deciding what the case is to hold. The overall design concept of the Little Dragon system proceeded as follows: First, the external shell is defined as an open-ended tube. Second, several interchangeable ends for the shell are designed. Third, custom motherboards are designed to fit the case. The Tube or Shell The shell for the Little Dragon designs is a rectangular tube 1 3 / 4 " (44 mm) high and 16 7 / 8 " (427 mm) wide. The initial tube is designed to fit a standard 800 mm rack. Other designs to fit shorter racks can be easily made, but with the reduced size comes reduced capabilities and a mixture of sizes in the rack that may lead to other problems. The tube is perforated with numerous holes to allow the use of many different components that may be mounted in the tube. It is expected that the number of holes in the case will be increasing constantly as requirements for mounting new devices are met. www.itox.com/1u/cooling/ One U cases have traditionally had a difficult problem with cooling. The small 40 mm fans simply do not move enough air to cool today s high performance processors. Provisions in the Little Dragon are made on both sides of the tube for mounting two high performance squirrel cage blowers, one on each side, towards opposite ends of the case. A standard 120 mm vertical spindle blower, 25 mm high will be used. The blowers are arranged for positive airflow into the case. The blowers have approximately the same air flow as 24 of the standard 4 cm fans used in traditional 1U cases. As a matter of reference, the relative outputs of the standard muffin fans commonly used in computers compared with the Little Dragon blowers is given by the following chart.
Air Flow Comparison Fan Blower Air Flow (CFM) 14 12 10 8 6 4 2 0 0 5 10 15 20 Back Pressure (mm water) Provision is made in the standard case for air filtering. If operating in a clean environment the filters can be removed to increase air flow (Especially as filters are rarely cleaned.) One blower will provide adequate amounts of cooling air for most configurations being contemplated for the Little Dragon system. The blowers, having moving mechanical parts will have the lowest MTBF of the system. Providing for two blowers gives a redundancy that will effectively double the system MTBF. Externally, the tube has "ears" in front that holds the case in the front of the rack. Two pins mounted in the rack support the rear of the case; these pins engage two supports at either side of the rear of the shell. This support is infinitely adjustable to provide for variations in the nominal 800 or 900 mm front to back dimension of standard racks. Optionally, the "ears" can be rotated 90 degrees and mounted in optional holes to hold the tube on a wall, parallel to the surface of the wall. Tube Options Slides -- A tongue and groove sliding rail can be mounted on either side of the tube to fit a matching piece. This is a small sized rail, much simpler than that normally used on traditional rack mount cases. The parts of the rail system mounted on the case will have gaps in the center of the case on both sides so as to not cover the fan openings. The traditional ball bearing slides would block the airflow to the side mounted cooling fans. This sliding rail is intended to ease removal of the case from the rack and to make aligning the case with the rear pins to insert the case into the rack easier.
Stacking Tray -- Where several Little Dragon systems are to be used without a rack, an optional stacking unit is available. Each unit effectively becomes a short rack that can be attached to the unit above providing for a "rack" of any size. Quick Disconnect Attachment -- This unit removes all rear-mounted connections from the case to allow the entire case to become a field replaceable unit (FRU). The QD Attachment is composed of two "boxes." One box is mounted on the rack; one box is mounted on the case. The two boxes are connected in normal use by heavy duty, selfaligning connectors that allow the replacement of a case from the front without having to disconnect interface cables from the rear of the rack. The Ends The open tubes are made into cases and systems by the closing of the ends of the tube with a selection of interchangeable "Ends" that provide the computing functionality. The nominal dimensions for each end are: Height: 1.75 (44 mm) Width: 16 7 / 8 (351 mm) Depth: 14.44 (367 mm) ½ of the available space in a tube. Blank End Module -- to close the case in systems where only one active end is in use. The blank adapter may be the same format as used with the disk storage module, that is, it may have the same knock out panels for the disk drives to eliminate the need for a separate part.. Twin Motherboard Server/Processor End Module This module provides for two completely functional systems at one end of the Little Dragon case. Note that each system has its own hard disk. Only a power supply and the physical case are shared. Today s power supplies are extremely reliable. It is far more likely that a system will fail due to the operating system locking up rather than a hardware failure. Motherboards for use with this module are defined later in this document. But for the most up to date information consult the Itox web site at http://www.itox.com.
A case has two ends. A Little Dragon end module fits into one of these ends. You can put a Twin motherboard module in one end and a second module in the other end. That gives you four independent servers in 1U of space. This is the Quad Dragon, and a single 42 U rack makes it theoretically possible to put 168 independent servers in one rack. PCI Card Expansion End Module This module, called the Dragon+ module, provides for an expansion capability for the Little Dragon systems. The actual amount of expansion is dependent on the particular motherboard. Note particularly the IF15 motherboard described below which provides for more expansion capability than any other 1U system. Storage End Module The storage module provides for one 5 ¼ and two 3 ½ disk drive bays, all with front access. Each of the drive bays will be provided as standard with a knockout blank to prevent EMI leakage if that bay is not used. The knockout blank on the 5 ¼ will incorporate a separate knockout panel to accommodate a standard external SCSI connector. This will be used in conjunction with a SCSI RAID controller that might be mounted in a PCI card expansion module (Dragon+). The 5 ¼ bay may contain either a CD-ROM, a combined CD-ROM/FDD or a removable 3 ½ hard disk drive. Likewise the 5 ¼ bay may be left un-used and this area might be used to make a connection to an external SCSI controller. The 3 ½ bay may contain a hot swap module for use with a SCA 2 hard drive (1 high), a standard non-removable HDD, or a floppy disk drive.
A mounting provision is made in the Dual storage module system for a CS15 motherboard to be mounted in the center of the system, as will be further described later in this document. Motherboards IF10 -- Provides for one full-length PCI expansion. The IF10 motherboard provides for a lower cost option (using the Celeron CPU) and for a higher performance option (Pentium III). The IF10 is based on the DFI CW27 but has been beefed up in reliability, RFI performance, and LAN functionality. The IF10 is used in the PCI wxpansion end module (Dragon+). The IF10 uses the Intel 810 chipset and has one on board LAN provided by an Intel 559 LAN chip. IF15 Based on the Intel 815E chipset, the IF15 provides for two full-length PCI expansion cards and for a PMC (PCI Mezzanine Card) to give a total of three PCI expansion cards. Two on board LANS are provided for using one Intel 559 and one Intel 562 LAN chips. The 815E can operate with a 133 MHz system bus driving the fastest Pentium III CPU s available. Alternatively, lower cost Celeron CPU s may be used to provide a very good cost/performance ratio. The IF15 is used in the PCI expansion end module (Dragon+). CS15 Also based on the Intel 815E chipset, the CS15 is a smaller format motherboard specifically designed for use in the Twin Motherboard Server/Processor End Module. The version of the CS15 used in the Little Dragon (specifically the CS15-0) has no expansion capability. The CS15 provides for a complete server on one motherboard with two on-board LANS and up to 512 MB of memory. Dual Processor A very high performance dual processor Pentium 4 based motherboard is being planned for 2001. It is intended that this board be used in the Little Dragons, but it is not yet known if this motherboard can be adapted into a 1U case. Network Attached Storage (NAS) System The NASty Dragon The NASty Dragon is a storage system designed to be attached to a network over a LAN. It is built using a standard Little Dragon chassis with a CS15 motherboard mounted internally.
The motherboard is mounted internally so that the IDE cables used to connect the (up to) four disk drives do not exceed their maximum allowed length of 45 cm (18 ). One of the 5 ¼ drive bays is used for a combination CD-ROM and floppy disk drive unit. The other 5 ¼ drive bay is used for providing the connectors to let the system talk to the outside world. NAS systems have become quite popular lately because they are specially designed to be easy to integrate into an existing network. Note that the NASty Dragon storage system is very similar in concept to the RAID system described below. The differences are: The NASty Dragon is much less expensive, because 1) it uses the CPU on the motherboard to provide the controlling function rather than a separate controller card, and 2) the IDE drives used are less expensive than the SCSI drives used in the RAID system. The NASty Dragon uses less rack space as it is self contained in a standard Little Dragon 1U chassis. On the other hand, the RAID system is faster, has greater capacity, and has hot swap capability for failed drives along with automatic recovery when a replacement drive is installed. Hypothetical Configuration #1 The following configuration is hypothetical in that it is intended to serve as an illustration of how the Little Dragon components may be configured to make a working web server system. Let s say you need to build a web server. First, how does the server connect to the web? One common way is to use a PCI card with a T-1 interface. This can be done with a Dragon+ PCI expansion end module. This leaves the other end of the Little Dragon empty. But you know you will need some servers, so let s put in a couple of servers using a Twin Motherboard End Module.
Case No. One A PCI card with a T-1 interface, and a system running load balancing software at one end and two servers at the other end. Case No. Two We know that we ll need more servers. Let s add four of them using two Twin Motherboard End Modules. (This configuration has been assigned the name Quad Dragon.) Case No. Three You know that you ll need some on-line storage. And since the data you ll be collecting is financial, we don t want to take any chances in losing it, so put in a RAID system. We can do this using a PCI card based RAID controller. And as before, we have the other end of the case available for a couple more servers. Case No. Four We have individual disk drives on each of these systems. But these are best used for local storage, loading the operating system, caching frequently used web
pages and so on. We ll use five SCA-2 Hot Swap SCSI disk drives of 36 megabytes or so each to go with our RAID controller. That s 180 MB in a 1U chassis. This particular configuration is marketed as the Dragon RAID. All in all, this system has: T-1 Interface Load Balancing System Eight Web Servers RAID Controller Five SCSI Drives This system would be suitable for approximately 20 million hits a month. And it s all in 4U of rack space! Now suppose your site is mentioned in Time Magazine or on NBC. The traffic to your site jumps to 50 million hits a month. Add three more Quad Dragons, and you re running 20 servers. Your boss decides to put a whole library of information on-line. Just add two more Dragon RAIDs and you have 15 drives in your RAID system for a total of just about a half a terabyte of storage. By adding a dozen servers and ten disk drives, you ve used another 5U of rack space. A total of 9U of rack space not even a foot and a half of space in the rack. Contrast that to using traditional 4U servers (YES, Itox makes them as well.) where you will get only 10 servers in a full rack. You re looking at three full racks to do what the Little Dragons do in 15 ¾ of space. Twenty Million Hits a Month? Such a configuration is very similar to that presently used by the Book-Of-The-Month Club to handle some 20,000,000 hits a month.
Fifty Million Hits a Month? Is Intel architecture, rather than Sun or one of the big name proprietary systems companies, suitable for big sites? The biggest, Yahoo, handles 625,000,000 hits a day, and they all are sent out using Intel CPU s. Hypothetical Configuration #2 The IF15 motherboard is planned to have a rather specialized third PCI "slot." This third slot will have a connector compliant with the PICMG PMC standard and is an expansion slot which is in the physical form of a daughter board, rather than the conventional PCI expansion card. This card is envisioned to be used only when a specialized application demands or allows the design of a special card. Some uses where the design of such cards might make sense would be: Numerous companies manufacture PMC cards and a modest range of standard cards is produced. SCSI controllers and LAN controllers seem to be the most popular. Such cards can be used in the Little Dragon systems when a third expansion slot is needed. In CTI applications where the Dialogic CT Bus or the H-100 bus would be required on each system to transfer information between expansion cards. A special PCI to H100 bus card would be used on each system so that both the individual motherboards and the voice processing cards in adjacent systems can communicate with each other. Comments on Redundancy The Little Dragon systems have been designed as the best possible compromise between reliability and cost. For just one example, the Little Dragon systems do not provide for redundant power supplies. Yes, power supplies fail, but so might any other component. Indeed, the most likely part of a system to fail is the operating system. The Little Dragon concept is to provide for redundant systems. If a processing module fails, the entire unit can be easily replaced. The unit can then be sent for repair. This concept is specially designed for use in today s co-location environment. The Little Dragon offers system level redundancy for computational units. If a unit fails, the system continues to operate, just at a lower level of performance. Even if the failure is the operating system, the failure of one unit does not cause total system failure. The Dragon RAID does provide for unit level redundancy. The risks of having critical data lost is simply to high to ignore.
Conclusion This document is intended to be an overview of the Little Dragon system as it is being developed. Knowing the goals of the systems concept enable designers, marketeers, and customers to better understand what is being designed. More understanding will enable a better appreciation of the design trade-offs that have yet to be made. As stated at the beginning, the Little Dragon system is in the development phase. It is expected that changes in the details given here will occur. The present plans are for the Dragon RAID with a storage module in each end -- to be the first to be brought to market. The Quad Dragon depends on the availability of the CS15 motherboard now scheduled for first samples in Q1 of 2001.