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De-duplication does not work as I was thinking

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I have 140GB of data on Win2k3 on local disk D:


I backup to a NAS storage.


Later, Installed Win2k8, copied all data to the other server. Installed retrospect client on Win2k8, modified the backup job in Win2k3 and just added the win2k8 client as another source for the backup job.


The backup job is the same in the win2k3 server, just added the new source.


I was thinking that Retrospect will look a the file in the win2k8 client, compare with the file that is already in the backup set and do not copy the file again since it is the same file.


So, here is my problem, how does de-duplication exactly work?


Should Retrospect compare the file in the backup set with the file in the source? And then come to the conclusion that is the same file?


Any help is welcome






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Retrospect does not have block-level deduplication. !!!


What Retrospect does is more correctly called single-instance storage.


According to the 7.5 manual, it relies on the name, size, creation date and modification date.


There are also a couple of options governing the degree to which it checks, namely, "Match source volume to Catalog File", "Don't add duplicates to Backup Set", and "Match only files in the same location".


It also applied only to files in the same backup set. That is, it doesn't work across different backup sets.


Finally, files in the OS directory always get recopied.


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Thanks for the comments, I'm just disappointed.


I was thinking that backing up the same file, to the same backup set but from different sources will trigger the de-duplication feature as spected.


Is there any solution? Or should I buy a new big backup media to solve the issue?



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