Browse Prior Art Database

Preventative Rewrites

IP.com Disclosure Number: IPCOM000120609D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 70K

Publishing Venue

IBM

Related People

Christensen, TC: AUTHOR [+3]

Abstract

Disclosed is a process that gradually and continually rewrites all of the data stored on a direct access storage device (DASD) within a given period, and repeats the process. This maintains the data at high strength and quality before continuous degradations from track misregistrations (TMR), erasures or shifts, can noticeably degrade the quality.

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This is the abbreviated version, containing approximately 52% of the total text.

Preventative Rewrites

      Disclosed is a process that gradually and continually
rewrites all of the data stored on a direct access storage device
(DASD) within a given period, and repeats the process.  This
maintains the data at high strength and quality before continuous
degradations from track misregistrations (TMR), erasures or shifts,
can noticeably degrade the quality.

      Some DASD systems have no process of restoring degraded data.
Some DASD systems rewrite data after it has degraded seriously enough
to have some degree of difficulty in the data recovery process.  The
disclosed system restores the data with a rewrite before any
noticeable degradation, thereby preventing more serious degradation
from compounded effects.

      Sectors that are rarely used and never rewritten, that are
adjacent to very actively written sectors, are significantly more
susceptible to the combination of track misregistrations from both
sides than sectors that are more commonly rewritten.  Sectors that
are written with very active seeks with short numbers of sectors
transferred are more likely to have residual misregistration than
sectors written within long blocks of data transfer, where the head
is well settled at the correct position.

      Although the above small degradations are not initially
serious, they increase the probability that a single, more
significant problem could cause irreparable damage to some data
sectors.  By gradually rewriting all the data of the file in a
controlled manner, the overall risks of damage to data can be...