I talked to my engeneer to verify as we were researching the product and we are currently using Iscsi so this is of great intrest to us (Though NFS is also under heavy review)

Netapps answer was fairly simple

1) Dedupe does work on block level storage (FC and iscsi) with block level deduplication content or netapp "Knowing" the content is irellivent as it is just block on disk and any 2 blocks reguardless of content that are identical get de-dupped (Not supporising as other backup technologies do the same thing with encrypted files)

2) To gain back the space from dedup you must uncheck the "space reserved" otherwise the lun reserves the space reguardless of it is consumed (and it wont be because of dedup), you then gain back the space by making more LUN's on that flexvol

3) The dedup happens on the flexvol level reguardless of if the LUN's are iscsi, NFS, FC or any mix of the 3

4) The hosts will never see the savings of block level storage so reclaiming the space needs to be done via #3

I have asked them to send the white paper my way but acording to their engeneers there is no major hurdle.

The ones that I have found out there

http://blog.scottlowe.org/2008/04/24/using-netapp-deduplication-with-block-storage/

http://blog.scottlowe.org/2008/05/20/provisioning-luns-for-use-with-deduplication/

http://communities.netapp.com/docs/DOC-1192;jsessionid=7177122E64AA32F30DD92CEE995AC70E

It appears to work just fine assuming you do the correct configuration ... all the documentation points that way.

Either way we are still looking twards NFS as the host is able to SEE that space reclimation (That and as we have an ISCSI network using software initiators it is not going to cost us more to do)

Jered Rassier

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