Browse Prior Art Database

Non-Volatile Storage Emergency Destage Performance Improvement

IP.com Disclosure Number: IPCOM000106476D
Original Publication Date: 1993-Nov-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Beardsley, BC: AUTHOR [+4]

Abstract

Disclosed is a method of improving the speed of the Emergency Destage of NVS (Non Volatile Storage). The method involves grouping records and tracks together and overlapping data transfer time with locate latency.

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This is the abbreviated version, containing approximately 59% of the total text.

Non-Volatile Storage Emergency Destage Performance Improvement

      Disclosed is a method of improving the speed of the Emergency
Destage of NVS (Non Volatile Storage).  The method involves grouping
records and tracks together and overlapping data transfer time with
locate latency.

      A DASD (Direct Access Storage Device) Control Unit contains an
NVS (Non-Volatile Storage).  The NVS Emergency Destage causes data in
the NVS to be written to Direct Access Storage Devices for permanent
storage.  The Direct Access Storage Devices store data sequentially
onto data tracks.  These data tracks are divided into groups of data
called records.  Since there are multiple read/write heads on an
access arm, multiple tracks can be accessed without moving the access
arm.  The group of tracks that can be accessed without moving the
access arm is called a cylinder.

      The speed of the Emergency Destage can be improved by taking
advantage of the physical layout of the Direct Access Storage Device.
Each transfer of data to the Direct Access Storage Device involves
selection of the DASD and an access arm motion and a rotational delay
(Locate).  By grouping these transfers together (rather than
transferring separate records), much of the time involved in
selection and locate can be eliminated.

      This algorithm groups records that belong to a common track and
also groups tracks that belong to a common cylinder together into one
data transfer operation.  In thi...