Browse Prior Art Database

Dynamic Reconfiguration of DASD Arrays in Response to Logic Failures

IP.com Disclosure Number: IPCOM000115834D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Ouchi, NK: AUTHOR

Abstract

Disclosed is a mechanism where data are moved among DASD devices in response to a logic failure to remove exposure to loss of data or access to data due to a second failure. Data are moved so that a second failure appears a single failures in multiple parity domains.

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Dynamic Reconfiguration of DASD Arrays in Response to Logic Failures

      Disclosed is a mechanism where data are moved among DASD
devices in response to a logic failure to remove exposure to loss of
data or access to data due to a second failure.  Data are moved so
that
a second failure appears a single failures in multiple parity
domains.

      In high availability systems such as DASD Arrays, the system
can be designed so that there are no single points of failure.  If
failures occur, the window of potential second failure can be reduced
by moving data to other DASD units to restore the ability to sustain
a failure.  The use of "hot standby" drives and reconstruction data
onto such a spare drive reduces the window of exposure to a second
failure to the time required for reconstruction.  In some electronic
or control elements of the DASD Array are shared among several DASD
units and if a element fails, these units may be only accessible thru
a second or back-up element.  Failure of this second unit may cause
loss of access to all of these devices.  Disclosed is a mechanism
that moves the data so that failure of the second element is
equivalent to loss of a DASD unit in several parity domains.  Thus,
failure of the second unit can be tolerated.

      In a DASD array, parity domains can contain two or more devices
that share common logic or other support elements as long as there
are two or more alternate means of supporting the devices.  However,
in...