incremental/delta backup

Ben Escoto
Thu, 04 Apr 2002 11:41:40 -0800

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>>>>> "GK" == Gautamjit Kanwar <>
>>>>> wrote the following on Thu, 04 Apr 2002 17:39:29

  GK> i need to write a remote backup software application (over the
  GK> internet like but i am having a real hard
  GK> time finding the algorithm for calculating the changed parts
  GK> since last backup (the delta).

  GK> it seems rdiff-backup uses the same technology internally, can
  GK> someone please point me to resources on the internet for delta
  GK> calculation and implementation.

rdiff-backup just uses the standalone diffing utility "rdiff" to
calculate signatures and deltas.  rdiff is part of the rproxy project
(see and uses the rsync (see
rolling checksum algorithm invented by Andrew Tridgell and Paulus
Mackerras.  See Tridge's dissertation at

for a discussion of the algorithm.

Ben Escoto

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