difference between duplication and deduplication?

Duplication is just making one more copy of your existing data. You can duplicate the data from disk to tape or vice versa. Most of the times people use duplication from disk to tape so that tapes can be sent offsite and in case of site disaster the data can be safe at other location.

Whereas Deduplication is a technology where it compresses the data and saves lot of space.Data deduplication is a method of reducing storage needs by eliminating redundant data. Only one unique instance of the data is actually retained on storage media, such as disk or tape. Redundant data is replaced with a pointer to the unique data copy. There are different dedup devices in the market now and they have different functionality.

There are lot of other things that you can get in dedeup devices now days and can check different vendor manuals for that

Example of deduplication - same Word document is emailed to 3 different users.

1st copy of Word doc is backed up. When it gets to copy 2, only a pointer to copy 2 is written, not the actual data. Same with copy 3.

Next day, a change is made of copy 2 by user 2. Only changed blocks of file will be written to backup destination, not the entire file. So, only unique data blocks are stored instead of multiple copies of the same data, thus eliminating redundant/duplicate data.

See: http://www.lmgtfy.com/?q=what+is+deduplication%3F

This is a definition for data deduplication

[Storage System] The replacement of multiple copies of data—at variable levels of granularity—with references to a shared copy in order to save storage space and/or bandwidth.

First thing to realise is that they are totally different and have no relation what so ever

Duplication is when a backup is copied (duplicated) so that you have a second copy of the backup (maybe the first is on disk and the second is on tape - but they are identical copies, just in a different place.

De-Duplication is, as has already been described, used when you perform a backup to a special de-duplication disk area and the data written identifies things that are the same so doesn't need to write all of it to disk.

So as your write the data if you back up a Windows 2003 Server the data is stored, although some parts of its system may have duplicates so not all have to be backed up - if you then back up another 2003 server the disk areas has seen most of the files before so doesnt need to hold them again and just keeps a record of them

This saves a lot of disk space and in some cases you can back up a whole server but not need to actually write anything extra to disk as it has all been seen before

Hiope this and the other excellent replies explains it for you

NO!

If a full backup is really 500GB and due to using de-dupe only 10GB of that 500GB need to be written to tape as all other files have already been seen then when that backup gets duplicated to tape the whole image is re-hydrated and 500GB gets written to tape

I have nothing more to say to you...

Chris Zimmerman from Symantec has responded to ALL of your recent posts in this reply: https://www-secure.symantec.com/connect/forums/what-archiving-netbackup#comment-6771101

It is very specialized compression - far more complex methodology

A few ideas here but all technolgies are different:

http://en.wikipedia.org/wiki/Data_deduplication

ok.what is dedup data?

and in duplacation ,there is no redundancy or compression?whole data is duplicated?

"eliminating redundant data"---what does that mean?