VMWare environment not seeing deduped space

[rdeuberry]

VMWare 5.1, NetApp 8.2.1

We have created several volumes and have moved our datastores over. The dedupe process has ran and we are seeing 40-50% savings! However vSphere does not recognize any of that free space and still shows the un-deduped amount for how much we are using. Some research led me to believe that disabling space reservation (essentially thin provisioning) would let vmware use the deduped space but that does not seem to be the case as we already have all of our LUNs setup in this manner and are not seeing the space. Any ideas?

[billshaffer]

I'm inferring that you've presented luns to VMWare for datastores?  If that's the case, what you see is expected - with block storage, the deduped space is available to the controller, but invisible to the host.  In other words, you've presented a 100G lun to VMWare.  VMWare knows how big it is, and knows how much has been written, which is what it reports.  VMWare doesn't know that the storage system has deduped some of the data - the controller sees that space savings, but VMWare still has the size of the lun, and the amount that has been written.  Since you have the space on the controller, you could grow the lun, thus realizing your increased capacity to VMWare.

https://communities.netapp.com/docs/DOC-1192 might explain it (the comments sum it up). 

Hope that helps

Bill

[rdeuberry]

Correct Bill, over FC. So when you say grow the LUN do you mean resize it to incorporate the % of the dedup savings? So for instance if I have a 2TB LUN with a 50% reduction in size due to deduping, I should make that LUN 3TB? I've tried several of the configurations in the above link but none of them have allowed vmware to see the deduped space.

[billshaffer]

I don't think you'll ever get VMWare to see the deduped space.  The link mentions where the freed blocks are returned to after dedupe - it is always the storage system side, not the client side.

You are correct in our interpretation of my "grow the lun" comment.  You still get to use the benefit of dedupe, it's just that VMWare doesn't see it.

Bill