Dedupe data size on tape after vaulting

[MohdAlim]

Hi

I have a query with the dedupe data size on tape after vaulting. Assuming I have a data size of 10GB (before dedupe). Subsequently, the data size after dedupe to disk is 1GB. When the dedupe data is vaulted to tape, will it retain the 1GB value or the data will be rehydrated back to 10GB?

[Marianne]

Duplication to tape will always rehydrate data - you will have 10GB data on tape.

[MohdAlim]

Assuming that I have a differential backup of 1GB before dedupe, and 500MB after dedupe. So when vault to tape, the size will be 1GB?

[Nicolai]

All writes to tapes will be the "full" size regardless of  previous de-dupe data size.

Remember tape is a sequential media - disk is random and since reading of de-dupe data require huge amount of random I/O, tape can't do the job.

De-dupe is more than just compression.

[Marianne · Accepted solution]

If you need written proof:

http://www.symantec.com/docs/HOWTO70654 :

Duplication jobs to tape rehydrate the data into the original NetBackup backup images...

[MohdAlim]

Thank you all for the info.