Browse Prior Art Database

Corrupted Sector ID Recovery Algorithm for Optical Data Storage

IP.com Disclosure Number: IPCOM000115729D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Lee, BS: AUTHOR [+2]

Abstract

Optical storage media is removable and exposed to the environment and is therefore more susceptible to damage. Damaged sector headers prevent the optical drive from reading data from that sector, even if the data is perfectly good. Tests have shown that sector header damage can be caused by aged media, media defects or contamination. This article discloses a means to recover data from defective sectors.

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

Corrupted Sector ID Recovery Algorithm for Optical Data Storage

      Optical storage media is removable and exposed to the
environment and is therefore more susceptible to damage.  Damaged
sector headers prevent the optical drive from reading data from that
sector, even if the data is perfectly good.  Tests have shown that
sector header damage can be caused by aged media, media defects or
contamination.  This article discloses a means to recover data from
defective sectors.

      The basic premise is to use good sector header information on
the disk to infer the address of sectors with bad headers.  A good
sector id must be found somewhere on the disk, before or after the
bad sectors.  Then one must be able to read a good sector mark at or
before the bad sectors.  This is usually possible because the sector
mark is stamped and has a high signal to noise ratio, so it can
usually be read even if the sector id is bad.

      Once a sector mark can be identified, one can infer when
subsequent sector headers occur: since the rpm is known, the clock
can be used to qualify when we expect the next sector marks to occur.
From this we can determine when we are at the sector header and then
when we are at the data region.  With this knowledge, we can stay in
synch and recover the data from the sectors.

      The drive can continuously read data from each sector as it
follows the spiral tracks.  By monitoring the tracking and focus
servo signals, we can guarantee that we haven't jumped track  or
missed sectors.  If we were able to read a...