Browse Prior Art Database

Changed Data Only Backup and Recovery

IP.com Disclosure Number: IPCOM000117566D
Original Publication Date: 1996-Mar-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 3 page(s) / 157K

Publishing Venue

IBM

Related People

Anglin, MJ: AUTHOR [+6]

Abstract

A program is disclosed that provides on a file basis a capability where, after an initial backup of an entire file, subsequent backup versions of the file consist of only the changed portions of the file, and where recovery of a file to a given version consists of restoring only the portions of the file that were changed since the given backup version was created.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 36% of the total text.

Changed Data Only Backup and Recovery

      A program is disclosed that provides on a file basis a
capability where, after an initial backup of an entire file,
subsequent backup versions of the file consist of only the changed
portions of the file, and where recovery of a file to a given version
consists of restoring only the portions of the file that were changed
since the given backup version was created.

      A file can be subdivided into one or more segments.  A physical
data repository is comprised of a collection of uniquely identifiable
segments representing non-volatile data storage available to an
operating system.  An operating system will normally write and read
file data in the physical data repository and record locator
information about the files that reside in the physical data
repository.  Identification of a file in the physical data repository
is accomplished by naming the set of segments in the physical data
repository that collectively represent the file.

      For each uniquely identifiable segment in the physical data
repository, there is a separate corresponding indicator in the
non-volatile physical data repository change map.  A physical data
repository change map indicator may have one of two states; either
'segment changed' or 'segment not changed.' added next sentence after
review The physical data repository maintains the physical data
repository change map.

      The non-volatile segment monitor change map contains an
indicator for each of the segments in the physical data repository
representing files that are being monitored for backup and recovery
purposes.  A segment monitor change map indicator may have one of two
states; either 'segment changed' or 'segment not changed.'  The
segment monitor maintains the segment monitor change map.

      The backup/recovery manager maintains a repository of file
segments and a database for tracking each file segment.  Each backup
for a file is a version.  The backup/recovery manager can maintain
multiple versions of any given file by recording for each version the
one or more file segments that have changed since the previous
version.  For recovery to a specific version, only the file segments
changed since that specific version are written to the current
version of the file.

      The interactions in this program are described below and are
depicted in the accompanying figure.
  1.  When the operating system writes file data to a given segment
in
       the physical data repository, the corresponding indicator in
the
       physical data repository change map has its state set to
'segment
       changed.'
  2.  To enable subsequent backup and recovery for a file, the
segments
       comprising the file are identified to the segment monitor.
When
       a segment not currently being monitored is identified to the
       segment monitor, the corresponding indicator in the segment
       mo...