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Patent Application Publication Sep. 9,2004 Sheet 6 of 6 US 2004/0177182 Al
EMBEDDED CONTROL AND MONITORING OF
HARD DISK DRIVES IN AN INFORMATION
BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention is related to information handling systems, and more specifically, to embedded control and monitoring of hard disk drives in the information handling systems.
 2. Description of the Related Art
 As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes, thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems, e.g., computer, personal computer workstation, portable computer, computer server, print server, network router, network hub, network switch, storage area network disk array, RAID disk system and telecommunications switch.
 Hot-swap SCSI disk drives may be used in RAID disk systems. These hot-swap SCSI disk drives are housed in a matching drive chassis or cage having a SCSI backplane (bus) which includes a SAF-TE (SCSI Accessed Fault Tolerant Enclosure) logic that provides an interface to the SCSI disk drives for the support of status signals, hot swapping drives, and enclosure monitoring. The SAF-TE protocol is an industry standard that allows the SCSI bus to be used for control and status purposes.
 The SAF-TE interface provides this industry standard, non-proprietary way for third party disk and RAID controllers to be automatically integrated with peripheral packaging that supports status signals (LEDs, audible alarm, LCD, etc.), hot swapping of hard drives, and monitoring of enclosure components. From the system vendor's point of view, this allows quick integration of the best third party controllers, knowing that they will fully integrate with disk and peripheral packaging. It also allows a selected controller to work with a variety of expansion packaging, being fully able to sense status and drive enclosure indicators. The cost of a separate cable and interface for enclosure services is also eliminated.
 SCSI is the underlying transport mechanism chosen for communicating enclosure information. This means that all standard SCSI host adapters will work. No special considerations, such as reserved signals on the SCSI bus, or additional cables are required. The SAF-TE Interface is implemented using a simple SCSI part and a microcontroller. The SAF-TE processor (SEP) device conforms to the ANSI SCSI-2 specification for processor devices.
 The SAF-TE processor has two interfaces, SCSI and I2C. The SAF-TE processor performs the SAF-TE target protocol entirely with its SCSI interface. A RAID on motherboard (ROMB) controller communicates with the SAF-TE processor to perform a number of operations. Since the SAF-TE processor is located on the SCSI backplane (bus), it also performs a number of embedded management functions, e.g., monitoring temperatures, voltage and fans, and reports that information to an Embedded Server Management (ESM) system via the I2C interface.
 When the SCSI backplane (bus) is split into two buses, for added speed, redundancy, etc., a second SAF-TE processor, commonly located on a SCSI daughtercard, must be added to the system backplane. Split SCSI backplane configurations separate the hard drives such that two separate SCSI channels may independently control the hard drives. However, since the SAF-TE protocol must be run on each SCSI bus, a separate SAF-TE processor is needed for each bus. Thus, the SCSI daughtercard serves this purpose in combination with the standard SAF-TE processor on the SCSI backplane.
 The cost of a SAF-TE processor on the SCSI backplane is not trivial. The SAF-TE processor also occupies backplane board space and restricts airflow ventilation through the SCSI backplane. Since the information handling systems are becoming more dense and total power consumption increases, any improvements in reducing power consumption, increasing airflow ventilation and/or reducing costs are very beneficial.
SUMMARY OF THE INVENTION
 The present invention remedies the shortcomings of the prior art by providing a method, system and apparatus for providing the functionality of a SAF-TE processor embedded on the SCSI backplane and also eliminates the need for SCSI daughtercards by utilizing functionality of the RAID (ROMB) controller and the Embedded Server Management (ESM) system already present in the information handling system. Remaining on the SCSI backplane are only sensors and input-output (I/O) registers as required. The I/O may be split between the ESM and ROMB according to functional requirements. The prior art SAF-TE processor functionality may be reassigned to the ESM and ROMB. For example, the ROMB may obtain information directly from the hard drives, e.g., revision number, vender ID, etc. The ROMB performs SCSI bus scans to detect hard drives during power-up of the information handling system. During power-up the ROMB enables power to all disk drive slots then removes power to empty slots after performing the SCSI bus scans.
 The ROMB may also obtain limited environmental sensor data from the SCSI backplane and/or housing. Typically however, the ESM handles the environmental data. Disk drive slot status, e.g., disk drive presence, drive
inserted, slot ready for insertion/removal of disk, slot operational, may be obtained by the ROMB by reading status bits over a serial channel between the ROMB and the SCSI backplane. The ROMB may write light emitting diode (LED) status, e.g., to drive LED blink patterns, to the SCSI backplane via the serial channel therebetween. The ROMB may also perform disk drive control, e.g., prepare for operation, insertion/removal and identify, by sending information to the SCSI backplane, via the serial channel, for the appropriate LED blink patterns.
 The ESM may support temperature/voltage warnings and errors from sensors sending their readings over, for example but not limited to, an I2C bus. The ESM may also read disk drive failure/OK status, e.g., general health of the disk drive, via the I2C bus. In addition, the ESM may receive SCSI cabling errors from, for example but not limited to, a SCSI daughtercard indicating that a correct disk system configuration exists.
 In an exemplary embodiment of the present invention, an information handling system has a ROMB and ESM interface in combination with operating management software, e.g., Embedded Server Management (ESM) software. A common way for ESM software to detect status information is for it to access the I2C bus(es) of the information handling system, and periodically poll these buses for the desired status information. The I2C bus specification, version 2.1, January 2000, is available from Philips Semiconductors, and is incorporated by reference herein. It is contemplated and within the scope of the present invention that any type of input interface hardware and protocols may be used in the present invention, so long as a desired status input may be recognized by the information handling system input devices and thereby read by the ROMB and ESM interface for processing thereof.
 In this exemplary embodiment, the SCSI backplane comprises a complex programmable logic device (CPLD) having at least two I2C interfaces and provides control signals for external components, e.g., hard disk drive power field effect transistors (FETs). In the addition, the CPLD may also be adapted to support secondary backplanes, e.g., 1x2 backplanes in peripheral bays. The ROMB controls hard disk drive power and the status, and indicator LEDs. The ROMB also may provide status to the ESM interface. The ESM interface is coupled to the sensors via an I2C bus and may have read-only access to the CPLD.
 In another exemplary embodiment of the present invention, external RAID cards may be supported with a daughtercard having a SAF-TE processor, e.g., an external RAID card controlling a split backplane.
 A technical advantage of the present invention is providing the functionality of a SAF-TE interface without the cost and complexity of adding another processor. Another technical advantage is providing SAF-TE functionality by using the existing ROMB and ESM in combination with a SCSI backplane, and serial and I2C interfaces therebetween.
BRIEF DESCRIPTION OF THE DRAWINGS
 A more complete understanding of the present disclosure and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings wherein:
 FIG. 1 is a schematic block diagram of an exemplary embodiment of an information handling system;
 FIG. 2 is a schematic block diagram of a prior art SAF-TE system;
 FIG. 3 is a schematic block diagram of a SAF-TE system of an information handling system, according to an exemplary embodiment of the present invention;
 FIG. 4 is a schematic block diagram of a CPLD used as I/O status and control on a SCSI backplane coupled to the ESM and ROMB depicted in FIG. 3;
 FIG. 5 is a more detailed schematic block diagram of the CPLD interface depicted in FIG. 4; and
 FIG. 6 is a schematic block diagram of a dual channel external RAID system, according to another exemplary embodiment of the present invention.
 The present invention may be susceptible to various modifications and alternative forms. Specific exemplary embodiments thereof are shown by way of example in the drawing and are described herein in detail. It should be understood, however, that the description set forth herein of specific embodiments is not intended to limit the present invention to the particular forms disclosed. Rather, all modifications, alternatives, and equivalents falling within the spirit and scope of the invention as defined by the appended claims are intended to be covered.
DETAILED DESCRIPTION OF SPECIFIC
 For purposes of this disclosure, an information handling system may include any instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, or other purposes. For example, an information handling system may be a personal computer, a network storage device, or any other suitable device and may vary in size, shape, performance, functionality, and price. The information handling system may include random access memory (RAM), one or more processing resources such as a central processing unit (CPU), hardware or software control logic, read only memory (ROM), and/or other types of nonvolatile memory. Additional components of the information handling system may include one or more disk drives, one or more network ports for communicating with external devices as well as various input and output (I/O) devices, such as a keyboard, a mouse, and a video display. The information handling system may also include one or more buses operable to transmit communications between the various hardware components.
 Referring now to the drawings, the details of exemplary embodiments of the present invention are schematically illustrated. Like elements in the drawings will be represented by like numbers, and similar elements will be represented by like numbers with a different lower case letter suffix.
 Referring to FIG. 1, an information handling system is illustrated having electronic components mounted on at least one printed circuit board (PCB) and communicating data and control signals therebetween over signal buses. In