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A Distributed Index Method with Fault Tolerance

IP.com Disclosure Number: IPCOM000013488D
Original Publication Date: 2001-Mar-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 2 page(s) / 95K

Publishing Venue

IBM

Abstract

Disclosed is a concept that distributes binary information used for servo index sector identification, across successive servo regions of a storage device, resulting in improved servo sector format efficiency and data reliability.

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A Distributed Index Method with Fault Tolerance

Disclosed is a concept that distributes binary information used for servo index sector identification, across successive servo regions of a storage device, resulting in improved servo sector format efficiency and data reliability.

We identify a servo index bit pattern, having a sufficient distance (d) property to an all 1's pattern, and all single bit shifts between the 1's patterns and servo index pattern, that will provide desired error correction and detection properties. For example, the 14-bit pattern in Figure 1 is minimum distance 7 when a 14-bit sample window is positioned over any bit of the pre-amble/post-ample/servo information.

____________

Window slide -----> | |

...111 00000110010100 111...

______

Index Sector Found ---> _______-_____|

Figure 1

A minimum distance of d allows up to s bit errors to be corrected and s + t errors to be detected according to the formula 2s + t [ d - 1. For instance, if d = 7, we can correct 2 errors and detect 4. Adjustments between correction and detection may be made according to performance requirements.

The chosen pattern is distributed between a pre-amble and post-amble pattern of 1's across successive servo sectors (Sn). Each bit of the pattern is placed in a fixed location within each servo sector. In the following example, the index bit is located after the servo track identification region (TID), before the position error signal (PES), for each of the 90 servo sectors.

S0..........S13 S14..........S18 S19........... S20 --> S26 ...........S27 S28..........