Electrical computers and digital data processing systems: input/ – Input/output data processing – Peripheral adapting
Reexamination Certificate
2000-06-22
2001-08-07
Lee, Thomas (Department: 2182)
Electrical computers and digital data processing systems: input/
Input/output data processing
Peripheral adapting
C710S018000, C710S031000, C709S241000, C709S201000, C711S113000, C712S036000
Reexamination Certificate
active
06272571
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to data processing systems and more specifically to a method and apparatus for enhancing the performance of magnetic storage devices under different operating conditions.
2. Description of Related Art
Data storage devices useful in digital data processing systems generally fall into different media categories. These categories can be ranked in terms of slowest to fastest response times as: (1) magnetic tape storage units; (2) optical storage units; (3) magnetic disk storage devices; and (4) digital random access memory (DRAM) storage devices. System administrators allocate different ones of these data storage devices or resources depending upon their relevance to a particular application.
Devices within a media category can also have different response times. This is particularly true with magnetic disk storage devices. In some situations the differences are a matter of mechanical and electronic design. For example, a smaller physical disk may have better performance than a larger physical disk due to reduced rotational latency in the smaller physical disk. Even within a common design, performance differences can be observed based upon file formatting or file structure. For example, monitored performance during reading operations may be reduced in a striped format versus a non-striped format because overlapping seek operations can be performed in a striped format. The performance in a mirrored system may be less favorable than in a non-mirrored system. In other redundant storage systems, access to data in a parity-based format may be degraded compared to access to data in a non-parity format.
In still other applications, a single physical magnetic disk storage unit or volume may contain multiple logical volumes. Such physical volumes are often called “hypered” volumes. In certain applications a non-hypered volume may exhibit better performance than a hypered volume, as when different applications make simultaneous accesses to the multiple logical volumes on a single physical volume. A log structured file format stores data in random, noncontiguous blocks on one or more physical disks.
A particular file, that is an application program or a related data file, may be stored in accordance with any of the foregoing formats or some combination thereof. For example, a logical volume may be stored in either a non-hypered, striped format or as a non-hypered, non-striped format.
Often times applications access data from locations sequentially. That is, an application may read or write data from or to a number of storage locations in sequence. With larger logical volumes this may involve transfers to or from a plurality of storage tracks in succession. In such operations attempts to read data in a logical volume with a log structured format produces the slowest response time. Conversely, if write operations are to random locations optimal performance may be achieved by storing the data in a log structured format.
With all the foregoing available diverse formats, it is difficult to predict which of these formats will produce the best overall performance. Typically, however, a system administrator uses a priori knowledge about anticipated operations to select one specific format. Hence the file or volume is optimized for the most likely operations, but will run sub-optimally for other operations. For example, if it is believed that random write operations will be the predominant mode of operation, a system administrator might select a log structured file format or a striped parity file format. However, if there are intervals at which sequential accesses will be encountered, the systems will run sub-optimally with respect, for example, to a mirrored, non-striped format. Notwithstanding this disadvantage, this continues to be the method by which the selection of a format for an individual logical volume or file is made.
SUMMARY
Therefore it is an object of this invention to provide a method and apparatus for improving the performance of storage devices in which data can be stored and processed according to different formats.
Another object of this invention is to provide a method and apparatus for enhancing the performance of a magnetic disk storage device that is capable of storing data in different formats.
Yet another object of this invention is to provide a method and apparatus that enables the data stored on a magnetic disk storage device to be processed in accordance with different formats according to particular requirements of an application.
The above and further objects and advantages are obtained in accordance with this invention by storing data in a first data block according to a first of a plurality of possible formats for operating in response to data transfer requests. A second data block is established for storing data in a second format. When a need for processing data in the second format exists, a copy of the data in the first format is transferred from the first data block to the second data block in the second format. Thereafter data transfer requests are directed to the second data block.
In accordance with another aspect of this invention, the performance of a data processing system comprises a first storage element of a given medium configured to store data according to a first format is improved by establishing a second storage element. The second storage element of the given medium has storage adapted to be configured according to a second format. In response to a predetermined event data from the first storage element is transferred to the second storage element to be stored in the second format.
In accordance with another aspect of this invention, the performance of the magnetic disk storage system that stores data in logical volumes is improved. The magnetic disk storage system stores a first logical volume of a predetermined size with a first of a plurality of possible formats and operates in response to data transfer requests in a first application. Performance is enhanced by establishing a second logical volume of a least a predetermined size for storing the data. Conditions are monitored to determine a time when a second application will process the data wherein performance of the second application would be enhanced if the data were stored in a second format. When that condition exists, data is copied from the first logical volume to a second logical volume in the second format. Thereafter data-transfer requests generated by the second application are directed to the second logical volume
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EMC Corporation
Herbster George A.
Lee Thomas
Peyton Tammara
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