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Method and Apparatus for Combining Independent Data Sectors Disclosure Number: IPCOM000124559D
Publication Date: 2005-Apr-27
Document File: 3 page(s) / 56K

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The Prior Art Database


This article describes a simple method for ensuring data integrity during interrupted writes when multiple sectors are combined into a single logical block

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Method and Apparatus for Combining Independent Data Sectors

Initial implementation of large block sector formats is likely to involve combining several independent physical sectors, each written using a current 512B sector format. For example eight 512B physical sectors could be addressed together as a single 4kB logical sector.

If a power failure were to occur while writing a logical sector comprised of multiple 512B physical sectors it is possible that some of the physical sectors might be successfully written with new data while the remainder retain the original data. Since each of the physical sectors has its own independent ECC and CRC these physical sectors would all be read as valid data. Without some additional mechanism to check the coherence of the logical sector as a whole it is likely that a large block logical sector comprising a combination of old and new data would be incorrectly reported as valid data. This is a data integrity problem.

If a power failure occurs while a logical 4kB sector is being overwritten we would like to be able to guarantee that when power is restored and the 4kB sector is read back one of three things happens : either the old data is read successfully, the new data is read successfully or the sector cannot be read and a read error occurs. It should not be possible for the drive to return a sector comprising some old data and some new data.

To acheive this requirement, the CRC for the logical 4kB sector can be constructed so that it spans all physical sectors in a single logica...