Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1999-02-08
2001-07-24
Choules, Jack (Department: 2177)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000, C360S086000, C360S090000
Reexamination Certificate
active
06266677
ABSTRACT:
BACKGROUND OF THE INVENTION
Data storage devices have methods to ensure the integrity of the data. In one method, called “read-after-write,” data is put onto the media, and is then immediately read to ensure that the data was correctly written. There is also a process that separately and non-automatically looks at the media and checks to see that it can be read back from the device. This disc verification is a utility (called ScanDisk) that can be used on current PCs.
The mechanism of read-after-write is disadvantageous in a slow device in that it takes a significant amount of extra time to run that process. For example, a CD has a much slower read and write speed than does a hard drive. The data rates for a CD for writing are something today between 300 and 600 Kbytes per second, and a hard drive is on the order of ten times faster than that. The reading speed of a CD is about six times faster than the writing speed, and a hard drive reading speed is the same as the writing speed. Thus, if the user needs to conduct an operation on a CD where data is written and read back, it will be significantly slower than if the user were able to simply write the data to the disc without verifying it. This is how the file system for CD currently works. Data is written but not verified.
When the user does a format operation to prepare a CD disc for taking data, the system typically writes to that disc to arrange where the data will ultimately be put and then verifies that the data is able to be read back. But after the data has been written, the user has no assurance that something hasn't happened to damage the disc between the time of format and the time of writing data. Any rewritable particular media will be used over a long period of time, and many things can happen to that disc. The disc can be scratched, get fingerprints and dirt on it, etc.—All of these factors will affect both the successful writing of additional data as well as reading of the data.
On a hard disk, the media is in a very controlled, sealed environment. You cannot put a fingerprint on a hard disk. You cannot get dirt on a hard disk. But a removable media is exposed to the environment, thereby making it more vulnerable to damage. CD media is particularly susceptible to this damage because it is the only rewritable media that does not have a protective case (i.e. audio tapes, VCR tapes, floppy disks, etc.) When a user does the formatting and verifying, the disc is physically secure since it is in a device away from fingers, etc. But when the CD is removed from the drive problems arise. This is a significant difference between hard disk and CD technology.
All data storage devices take advantage of error correction designed in the format. There are many error correction algorithms. They are all effective in correcting errors and defects, but every method has limitations. A thick thumb print on a CD disc, for instance, will render sections of the CD disc unreadable. Since this type of reusable media is in a very unprotected environment, it will be handled and is likely to become soiled and damaged at random times over a long period of time. Therefore, a method is needed to ensure the steadfastness of data integrity.
SUMMARY OF THE INVENTION
These and other objects, features and technical advantages are achieved by an improved system and method which automatically performs disc verification on the disc without any user intervention. It would run at appropriate intervals, determined by looking at certain parameters of the disc, in order to insure a minimum risk of either data unreadability or data being written on a location unsuccessfully. The improved system includes the error correction processes that currently apply to CD's, but the algorithms will look at the disc and the usage of the disc, in particular, how much the disc has been handled by a user. It will then determine the appropriate time to automatically run the disc verification function and repair of the disc.
One of the features of the error correction on a CD as compared to a hard disk, is that a hard disk will only tell the user whether the data is good or bad. Either the ECC worked or it did not work to correct the data. CD technology typically set a threshold on how much ECC is used before informing the system to relocate the data because of risk of lost data. CD technology also typically allows for the system to inquire how much ECC was used to read the data. The improved system uses this method of inquiring how much ECC was used to intelligently determine if disc verification is required.
Since the process of assessing, cleaning up the disc, and relocating data is done in the background, this system achieves additional protection without having to do a read back after the write process. Consequently, the improved system gains the performance of a write-it-and-go-on device, while preserving the protection of being able to check the disc at regular and appropriate intervals.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.
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“Predictive Failure Analysis Of Hardware Errors”, IBM Technical Disclosure Bulletin, Armonk, NY, vol. 35, No. 1B, Jun. 1992, pp. 323-324.
“Predictive Failure Analysis Of Reassign Rate”, IBM Technical Disclosure Bulletin, Armonk, NY, vol. 35, No. 1B, Jun. 1992, pp. 325-326.
Rodgers Andrew J
Taugher Lawrence N
Choules Jack
Hewlett -Packard Company
Lewis Cheryl
LandOfFree
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