Browse Prior Art Database

Raid with Automatic Defect Detection and Correction Functions

IP.com Disclosure Number: IPCOM000117429D
Original Publication Date: 1996-Feb-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 78K

Publishing Venue

IBM

Related People

Iwata, K: AUTHOR [+3]

Abstract

Disclosed is Redundant Arrays of Independent Disks (RAID) which have functions to detect media defects and correct them automatically. With these functions disk arrays can avoid undesirable situations in which lost data can not be recovered when one of the drives is failed.

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Raid with Automatic Defect Detection and Correction Functions

      Disclosed is Redundant Arrays of Independent Disks (RAID) which
have functions to detect media defects and correct them
automatically.  With these functions disk arrays can avoid
undesirable situations in which lost data can not be recovered when
one of the drives is failed.

      The RAID disk arrays with conventional technology do not have
means to detect media defect (Fig. 1).  In this example, one of the
drives (say HDD 1 (1)) has a defective sector(2) which can not be
read by the RAID controller.  The RAID controller, however, does not
know that there is a defect on HDD 1(1) because there is no means to
detect such a defect.  Suppose HDD 5(3) fails, then the RAID
controller enters into an "one drive failed mode" where process of
host command should avoid failed HDD 5(3).  With this situation, if
host computer accesses defective sector(2) in HDD 1(1) or
corresponding position (4) on failed HDD 5(3), the RAID controller
cannot provide the requested data to the host computer.  The RAID
disk arrays with disclosed method avoids the above problem as
following manner.  The RAID controller has a function to check media
defect and consistency of parity data of the hard disks which form
the disk array.  The checking function can operate as a "background
mode" which works concurrently with process of the read/write access
command issued by a host computer.  The media defects found by the
checkin...