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| Asynchronous digital time-division multiplexing system with distributed bus |
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Apparatus and method for providing a transparent disk drive back-up
| Details |
Inventors: Gunderson, Dick;
Assignee: DuoCor, Inc. (Nevada City, CA)
Primary Examiner: Chan; Eddie P.
Assistant Examiner: McLean; Kimberly
Attorney, Agent or Firm: Thomas, Kayden, Horstemeyer & Risley
A method and corresponding apparatus provide a backup drive in a computer system having a CPU, a memory, an operating system executing between the CPU and the memory, and a first and second storage device. In accordance with one aspect of the invention, the method includes the steps of designating the first storage device as a primary drive and designating the second storage device as a backup drive. It further includes the step of making the backup drive appear invisible to the operating system. Preferably, the invention accomplishes this step by writing a specified value to the device identification location (address 01FE and 01FF of the boot sector). Thereafter, the invention writes data from the primary drive to the backup drive on a periodic basis, using direct basic input/output service (BIOS) calls. It will be appreciated that, since the drive is "invisible" to the operating system, that direct BIOS calls are required in order to write data to, or read data from, the backup drive. Finally, the invention includes the step of redesignating the primary drive and the backup drive upon receiving a control command. The control command could be a user initiated command, or it could be automatically generated upon error detection. For example, if the system detects a fatal error on the primary drive, it may generate a control command that prompts the invention to redesignate the primary and secondary drives. This is accomplished (basically) by rewriting the values stored in the device identifying locations, thus making the backup drive now visible to the system and the primary drive invisible. |
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Having summarized various aspects of the present invention, reference will now be made in detail to the description of the invention as illustrated in the drawings.
While the invention will be described in connection with these drawings, there is no intent to limit it to the embodiment or embodiments disclosed therein.
On the contrary, the intent is to cover all alternatives, modifications and equivalents included within the spirit and scope of the invention as defined by the appended claims.
In this regard, the concepts and examples shown should be considered as exemplars of the principles, rather than as limitations on the system or method of the invention.
FIG.
1 shows a block diagram of a portion of a typical architecture in a personal or home computer system in which this invention could be used.
While four fixed hard disk drives are illustrated in the system, other embodiments of the present invention include two, three, five, six, and even greater numbers, limited only by the addressing capabilities of the system architecture and the resident operating system.
In still other embodiments, the devices 1, 2, 5, and 6 may be disk partitions instead of physical disk drives.
The first drive 1 is denoted as the primary boot drive, from which the computer boots itself on powering up.
That drive is shown configured as a "Master" on a first drive channel 3, which is connected to a primary disk controller 4.
Certain system architectures include data or drive channels on which it is possible to connect two or more disk drives or other storage devices, such as Compact Disc--Read Only Memory devices (CD-ROMs), or removable disk drives.
An example of one such drive channel is an Integrated Device Electronics (IDE) channel found on many personal computers.
An IDE channel can accommodate two devices on a channel, with one designated as "master" and the other designated as a "slave".
The designations are frequently set by jumpers on the devices themselves, or in more recent systems, they are configured in the computer memory itself, as part of the Basic Input/Output System (BIOS), when a system set-up program is accessed from Read-Only Memory (ROM) on system start-up
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I/O Systems 
