Electrical computers and digital data processing systems: input/ – Input/output data processing – Peripheral adapting
Reexamination Certificate
1998-07-07
2001-11-27
Lee, Thomas (Department: 2182)
Electrical computers and digital data processing systems: input/
Input/output data processing
Peripheral adapting
C710S052000, C710S065000, C360S048000, C711S111000
Reexamination Certificate
active
06324604
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to data processing systems and more particularly to magnetic media storage systems used in such data processing systems.
2. Description of Related Art
Many data processing systems include one or more central processors and one or more magnetic media storage systems. Typically, the magnetic medium comprises either a magnetic disk or a magnetic tape. Magnetic disk media storage systems, particularly, have been developed for use with particular machines according to particular data structures or formats. IBM mainframe computers constitute one such machine. UNIX-based or open systems constitute machines characterized by another diverse data structure.
For purposes of understanding this invention, one such characteristic is the relationships among a drive, the number of cylinders on a drive, the number of tracks in a cylinder, number of sectors in a track, the number of data blocks in a sector and the number of bytes in a data block. For example, Unix computers and the like operate with a data structure in which a data block comprises 512 bytes. Certain disk storage systems for Unix-based data processing systems, such as those supplied by the assignee of this invention, further arrange eight data blocks into one sector and eight sectors into one track.
Other computer systems exist that utilize host processors for operation with other, diverse data structures in which block sizes contain a different number of bytes. As one example, a host may operate with 2,088 bytes in a block. However, the market for magnetic disk storage devices for such data processing systems is limited, and the costs of adding such storage systems that are specifically designed for such data structures can be prohibitive. Likewise, rewriting applications to conform to another data structure is also prohibitive.
One might consider reformatting a standard device with the data structures characteristic of the host system. However, it has been found that this is difficult or impossible to accomplish primarily because magnetic disk storage devices themselves, even at the most basic levels, have been designed around standard data structures and can not be adapted to non-standard structures. Consequently, there has been no approach for integrating such standard magnetic disk storage systems into such non-standard data processing systems in a way that is transparent to input/output requests from a host with diverse data structures. However, as storage requirements increase, the demand for additional magnetic disk storage that operates with such hosts also increases.
SUMMARY
Therefore it is an object of this invention to provide a method and apparatus whereby a disk having a first data format can operate with a host characterized by a diverse data structure.
Still another object of this invention is to provide a method and apparatus whereby a disk having a first data structure can operate with a host in which applications programs operate with a second, different data structure.
Still another object of this invention is to provide a method whereby a disk having a first data structure can operate with hosts characterized by diverse host data structures in a manner that is transparent to any application program on any host.
In accordance with this invention input/output requests are processed in data processing system including a data storage device that stores data in fixed-length disk data blocks of a first plurality of data bytes and wherein a host generates input/output requests using fixed-length host blocks of a second plurality of data bytes. A buffer, intermediate the host and the data storage device has a size that exceeds the size of the larger of the host and disk data blocks. Data transfers between the host and the buffer occur in blocks corresponding to the size of the host data blocks. Data transfers between the data storage device and the buffer occur in blocks corresponding to the size of the disk data blocks.
In accordance with another aspect of this invention a data processing system includes a magnetic disk storage device having a characteristic fixed-length disk block size and includes a host that issues input/output requests including references to fixed-length host blocks of a larger size. A buffer is defined in a cache memory that has a size that is at least the size of the host block for storing an integer number of disk blocks whereby a set of the disk blocks is capable of storing a host block. A host adapter, that is connected between the host and cache memory, processes input/output requests from the host by transferring data between the host and the buffer in host blocks. A disk adapter connected between a magnetic disk storage device and the cache memory processes input/output requests in the buffer by transferring corresponding sets of disk blocks between the buffer and the magnetic disk storage device.
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Don Arieh
Ofer Erez
Vishlitzky Natan
EMC Corporation
Herbster George A.
Lee Thomas
Park Ilwoo
Pearson & Pearson
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