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Mechanism for Uniquely Identifying Logical Block Addresses Without Utilizing a Lookup Table on Reads

IP.com Disclosure Number: IPCOM000013506D
Original Publication Date: 2000-Aug-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Abstract

There are certain situations when a customer Logical Block Address (LBA) requires special handling. To perform any special handling on a LBA, a mechanism is needed to uniquely identify the LBA. The first thought that may come to mind is to place a unique data pattern on the LBA and restrict any customers from using this data pattern. This is an un-realistic restriction for customers, and therefore is typically not utilized. Another typical approach is to place unique LBAs in a lookup table. Each time a customer requests a data transfer, the lookup table is checked to see if any of the requested LBAs are listed. If they are, the special handling function is completed. If not, the data is transferred normally. There is a major performance drawback with using a lookup table to store information about unique LBAs. Prior to transferring data from any LBA, the lookup table must be scanned to determine whether the requested LBA is present. The time required to complete the lookup table scan results in a direct performance penalty for the customer. If the table scan is done in software, the performance penalty can be severe. The performance for accessing all LBAs is penalized in the lookup table scheme for what may be only a few LBAs that require special handling. This invention allows the unique identification of LBAs without compromising data access performance.

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  Mechanism for Uniquely Identifying Logical Block Addresses Without Utilizing a Lookup Table on Reads

    There are certain situations when a customer Logical Block Address (LBA) requires special handling. To perform any special handling on a LBA, a mechanism is needed to uniquely identify the LBA. The first thought that may come to mind is to place a unique data pattern on the LBA and restrict any customers from using this data pattern. This is an un-realistic restriction for customers, and therefore is typically not utilized. Another typical approach is to place unique LBAs in a lookup table. Each time a customer requests a data transfer, the lookup table is checked to see if any of the requested LBAs are listed. If they are, the special handling function is completed. If not, the data is transferred normally. There is a major performance drawback with using a lookup table to store information about unique LBAs. Prior to transferring data from any LBA, the lookup table must be scanned to determine whether the requested LBA is present. The time required to complete the lookup table scan results in a direct performance penalty for the customer. If the table scan is done in software, the performance penalty can be severe. The performance for accessing all LBAs is penalized in the lookup table scheme for what may be only a few LBAs that require special handling. This invention allows the unique identification of LBAs without compromising data access performance.

Most data channels in hard disk drives contain hardware that randomizes the data stream before it is written to the media. The data is then un-randomized when it is read back from the media. This hardware is referred to as the randomizer. The randomizer provides a programmable feedback pattern to be used during media accesses. The intent is to use different feedback patterns on consecutive tracks and cylinders to provide additional data randomization from track to track. Ultimately, this improves the integrity of the customers data. Normally, the randomizer is always enabled to provide customers the highest data integrity. This invention involves disabling the randomizer when special handling on LBAs is required. If it is decided that a particular LBA will requires special handling, the data channel randomizer should be disabled and the LBA can be written with whatever unique data pattern is desired. This will be referred to as "marking the LBA". The data channel randomizer is then re-enabled and restored to its original setting. When the customer attempts to read da...