Patent Application
20080082706
The subject matter which is regarded as the invention is particularly pointed out and distictly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains the preferred embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
In general, in exemplary embodiments, SCSI cables are coupled to SCSI adapters without the use of jumpers or dip-switches, to support multiple different configurations. Power control, data flow and drive addressing are automatically controlled and detected. Multiple combinations and configurations are possible with one or two adapters to each repeater card. Multiple repeater cards can further be daisy-chained to allow more drivers on the SCSI bus to the adapter. A given drive drawer can be powered on if any of the adapters are powered on and providing term power, which is provided by the adapter cards or any of the SCSI devices.
As discussed further in the description below, unused or reserved pins of a SCSI cable can be implemented to detect that two repeaters have been daisy chained Configuration is accomplished by comparing voltage levels on the unused or reserved pins, which are connected to a daisy-chained card or SCSI initiator port. In addition, the pins can be used to provide support so that so long as one or more adapters are powered on, the two daisy-chain repeaters remain turned on. Therefore, adapters may be powered on or off in any order. Furthermore, adapters that are powered off also have their repeaters turned off to allow concurrent maintenance of those adapters and repeaters.
It is therefore appreciated that each repeater in a SCSI drawer may be turned on or off by a SCSI adapter providing term power or by detecting that the repeater is tied to another repeater in a daisy chain configuration. If the daisy chain configuration is detected, one of the drive bays shifts it's SCSI IDs to avoid SCSI ID conflicts.
An extended SCSI bus 220 is coupled to repeater modules 210, 215. Extended SCSI bus 220 is coupled to target devices 225. Similarly, an extended SCSI bus 320 is coupled to repeater modules 310, 315. Extended SCSI bus 320 is coupled to target devices 325. While a plurality of hard disk drives are schematically depicted in
In one implementation, SCSI bus includes a multi-pin cable as understood by one skilled in the art can include 68 pins as in the case of a SCSI B cable, for example. Several pins remain unused. In exemplary embodiments, two unused pins can be implemented for automatic control as discussed. For example, pins 19 and 53 can be used. However, it is understood that other unused or modified pins can be used in other exemplary embodiments. For example, reserved pins 53 and 19 may be used.
By connecting two of the unused pins and corresponding wires from the SCSI bus, and monitoring the term power signals, automatic detection of the presence of additional repeater cards on the bus can be detected. Referring still to
Therefore, in exemplary embodiments, as discussed further in the description below, each set of SCSI devices 225, 325, which have their unique SCSI IDs, can have their IDs automatically shifted depending whether or not the devices 225, 325 are in use. For example, devices 225, 325 can have SCSI IDs 0, 1, 2, 3, 5 when in use individually. However, if devices 225, 325 are in use together, devices 325 can have their IDs automatically shifted to 8, 9, A, B, C, D. It is therefore appreciated SCSI target device 325 may be selectively cross linked to SCSI bus 220 for access by first host device 200 by automatically altering the SCSI ID of those devices such that no duplicate SCSI IDs are present within the combined bus.
Two unused wires on existing SCSI cables can be used in conjunction with SCSI repeater card circuits that sense if they are connected to another SCSI repeater card or host system. The circuits sense which ports are connected to servers that are powered on and enable the appropriate repeater modules. The SCSI repeater cards sense the voltages on the two wires to determine if they are the first or second card in a daisy chained SCSI bus. The card also senses which position it is in the disk drawer to set the repeater enable bits and addresses. The following is a truth table showing the card power status and enable bits for the repeater modules (see
Similarly when a single initiator card is cabled to a dual initiator card, the drive addresses are switched from 5, 4, 3, 2, 1, 0 to D, C, B, A, 9, 8 for some configurations in the disk drawer, as described further below. The following Figures illustrate exemplary embodiments of SCSI drawer applications.
As described above, embodiments can be embodied in the form of computer-implemented processes and apparatuses for practicing those processes. In exemplary embodiments, the invention is embodied in computer program code executed by one or more network elements. Embodiments include computer program code containing instructions embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other computer-readable storage medium, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. Embodiments include computer program code, for example, whether stored in a storage medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. When implemented on a general-purpose microprocessor, the computer program code segments configure the microprocessor to create specific logic circuits.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
