# zvol size and expanding



## xy16644 (Aug 12, 2014)

I would like to create a zvol on my one pool which will be used with iSCSI and a Windows 8 client. The only problem is that I am not sure what to make the size of the zvol. Currently the pool has 1TB of disk space (of which 800GB is free) but I know later on I would like to expand the pool so that is has 6TB of disk space and would like the zvol to use a good chunk of that new space.

So is the correct way to do this to use thin provisioning, or more properly as its called by ZFS, sparse volumes? 

`zfs create -s -V 5tb tank/thinvol`

I assume that when I open Disk Management in Windows (once added via iSCSI) it will see a 5TB partition? But on the server it will only show what space it is using? Obviously I can only use up to 800GB of space with the current disk I have but when I add more disks then I assume I could use all 5TB.

Am I understanding this correctly?


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## usdmatt (Aug 13, 2014)

Yes, you are correct. You can over-provision sparse ZVOLs and build the pool up afterwards.
I think you just need `-V 5t` without the 'b' in the create command although ZFS may just ignore the `b`.


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## xy16644 (Aug 13, 2014)

Thanks for confirming my thoughts on this. I have never worked with zvols so wanted to double check.


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