Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
1999-12-14
2003-04-22
Hudspeth, David (Department: 2651)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C711S004000
Reexamination Certificate
active
06553458
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to computer storage systems, and in particular to an integrated redundant storage device.
2. Description of Related Art
Computer installations and usage have become commonplace in business and home alike. Storage of large amounts of data and programs is required to perform the complex data manipulation and analysis.
Typically, data is stored on hard drives. These hard drives are typically standalone units that can store hundreds of gigabytes (GBs) of data. However, if the drive fails or crashes, the information stored on the hard drive is lost.
Solutions to this single point failure have incorporated several approaches. One approach is to provide a Redundant Array of Inexpensive Devices (RAID) which uses each device or hard drive to store portions of the data in a redundant fashion. RAID has several “levels” of redundancy, which provides additional protection for the data stored on the hard drives. The RAID approach uses expensive external array controllers to manage multiple hard disk drives in a redundant fashion.
A second approach makes use of inexpensive adapter boards that reside on the host computer's I/O bus to manage multiple drives in a redundant fashion. Another approach makes use of software drivers in the host computer to implement protected storage.
The problem with the RAID external controller approach is the expense and difficulty of housing the RAID controllers. The RAID controllers are large and powerful to allow the cost of the RAID to be amortized over the largest number of drives. The resulting storage systems are often more expensive than the host computer systems to which they are attached.
The I/O adapter approach circumvents the RAID problems by placing the controller within the host computer, thus using existing power and mechanical subsystems. However, since I/O slots are typically limited, numerous drives are again attached to the computer system. Additionally, the I/O approach cannot tolerate the failure of the host computer system due to the tight integration; critical disk state information needed for sharing the storage with another host computer is lost when the host fails. This eliminates this approach for anything but single host systems.
The software driver approach also makes use of the host computer system's computational and I/O resources to implement the data redundancy algorithms. This is the lowest cost approach, but results in a system performance degradation that is typically not acceptable. This approach also suffers from the disadvantage of the I/O adapter approach, namely, that critical disk state information is lost when the host fails, eliminating the ability to share the storage among multiple host computers.
All of these approaches suffer from degradation of the performance of the system when contrasted with the performance available from the storage incorporated into such systems. This is due primarily to the sharing of resources needed to implement protected storage among a large number of disk drives.
It can be seen, then, that there is a need in the art for redundant storage capability. It can also be seen that there is a need in the art for redundant storage capability that does not degrade system performance. It can also be seen that there is a need in the art for redundant storage capability that is inexpensive to implement.
SUMMARY OF THE INVENTION
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses an apparatus and method for providing selectively redundant storage within a computer. The device comprises a first storage device having a first form factor and a first height, a second storage device having the first form factor and a second height, coupled to the first storage device, such that the first form factor, first height, and second height allow the first storage device and second storage device to fit within a standard cage of a computer, and a controller, coupled to the first and second storage device, for selectively storing data on the first storage device and the second storage device, wherein the controller interfaces to the computer and presents the first storage device and the second storage device as a single storage device to the computer.
The method comprises coupling a first storage device having a first form factor and a first height to a computer through a controller, coupling a second storage device having the first form factor and a second height to the computer through the controller, such that the first storage device and the second storage device comprise a single storage device for the computer and fit within a standard cage of the computer, storing data on the first storage device based on instructions received from the controller, and storing data on the second storage device based on instructions received from the controller.
An object of the present invention is to provide redundant storage capability. Another object of the present invention is to provide redundant storage capability that does not degrade system performance. Another object of the present invention is to provide redundant storage capability that is inexpensive to implement.
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Gates & Cooper
Hudspeth David
NCR Corporation
Tzeng Fred F.
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