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Number   :  4191
Date     :  2003-04-02
Author   :  Garry Deane
Subject  :  Re: Delta-Byte Replication
Size(KB) :  1


--- In xxcopy@yahoogroups.com, "agressiv99"  wrote:
> What would it take for "delta-byte" replication to work?
> 
> That is, if I have a 700MB file, and 10MB in the file
> change. All command-line utilities will copy the 710MB
> file at that point.
> 
> We have some serious WAN implications, and backing up
> these large files everynight just because a few megs
> change really kills us.
> 
> Any ideas on the feasibility of this?
> 
> Greg

The low-tech answer may be to simply zip the file before backing it 
up. Large files like that are often database type files which are 
fairly effectively compressed. Our mssql database compresses to about 
15% of it's original size.

For a more high tech approach, we use an internet based backup 
solution which incorporates "delta-byte". This examines the changes 
that have been made to a file and only transmits a compressed change 
file. The old file is updated with the changes at the server end to 
create the copy of the new file. See this link for more information 
on the complete package (we only use the client software).

http://www.online-backup.com/datasheets/product.html

One word of caution is that certain types of data files can cause 
the "Fastbit" algorithm to choke. I have experienced some very long 
delays (hrs) while a file as small as a couple of Mb was examined. If 
you are considering that package, I suggest that you test it 
thoroughly with your particular data beforehand.

Garry



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