We are in the process of evaluating a new SAN machine for our data center and are in contact with various vendors. Their pre-sales guys seem to be pitching the one option quite aggressively while mentioning the others just in passing and that jewel of the crown is "De-Duplication", which means that if you have identical blocks on the SAN disks, then SAN would only store one copy of it and will save you space.

In every presentation I sit through, I get hammered by these guys about this chic new feature and they spend more than half a time on this and in remaining time,they wink and refer to other features as cool but not so cool as "De-Dup".

I plan to use the half part of SAN as shared storage for my RAC, while the other part for the RMAN backups. Now I am at loss because:

1- I don't think that my database would have too many identical blocks (if any), and if they are there, then we need to seriously re-visit the database design, instead of 'De-Duping.'

2- RMAN doesn't back the empty blocks.

So, apparently, there won't be many identical blocks on my SAN.

So how De-Dup is the silver bullet for my requirements?

I am afraid to ask the pre-sales guy as they are too enthusiastic to be interrupted and besides I am in the habit of heart-breaking.