Can we get the report of space used of guest VMs from Vcenter?

Nodes being polled via basic polling will not be storing disk space metrics, those are features of vman so if you do build the custom report it will be missing the data from the unlicensed systems. 

If you happen to have an unlimited license in SAM you could try to pull in the vcenter performance counters from there, but its an EXTREMELY manual process.  You would have to create a component one by one for each metric you try to collect on each vm.  That feature made more sense in the old days before VMAN was available and most people don't really use it much at all anymore.

Thanks for the details.. component method also wont work for me as the number of guest VMs are too many...

Will try to somehow convince customer to upgrade VMAN in order to meet the requirement.

I was wondering about this myself recently (about VMAN).

Currently, we have Storage Manager (or whatever its called nowadays) and we get daily and weekly reports that shows current usages and predicted capacity.

So, Pratik: Look into the Storage Manager product, I believe this would get you the reports you are wanting.

Update: I missed the part of your post about your customer. I would still pitch it to them and see if it is something they wanted to budget for.

we actually convinced them for upgrading VMAN licenses.... SRM would not fit in current environment so cant pitch that... thanks for the note...