SOLVED Windows Server - iSCSI Thin Provisioning issue

[Ralms]

Hi there,

I've configured a iSCSI target in my TrueNas box (12.0-U3.1) and it's using as its Extend a Zvol with Sparse (thin-provisioning) enabled.

I'm then consuming this target on a Windows Server Core 20H2 box.

Everything is working ok, however there is an issue, where I'm unable to Initialize the Disk in Windows because it has a capacity of 16KB (the block size is set to 16KB btw).

As such, I can only think of either:

1. Windows is not detecting the vol max size correctly.
2. TrueNAS is not providing the correct Metadata.

Something I've noticed is that when configuring the Extend, TrueNAS also is not identifying the max size of the volume:

Instead is marking it as a 16K volume.
(Venus is my Pool name)

Is this a bug?

How can I have Thin-Provisioning to work with iSCSI?

Thank you.

EDIT:
Here is the volume configured in Venus Pool

 

[Ralms]

Ok, this really looks like a bug.

I managed to find a trick to make it work.

After the Volume is created, the option to set if its "parse" mode or not, is not available when you try to edit.

So, what I've done was just "Edit ->Set a Size for this zvol" and defined a value.
I've picked the same Sync (Standard), same Compression level as before (Lz4 in my case) and Dedup off as before.
Something strange, is that the Zvol name in the edit screen was incorrect, was strange, but didn't affect anything.

TrueNAS allowed me to save this change.

After this, without changing ANYTHING on iSCSI, the Extent updated automatically and the Windows Server client machine also was seeing the new size set:

However, somehow, Sparse (Thin-Provisioning) remained set, so when I check the volumes, is still only using the dynamically allocated space:

Hope this helps someone trying to achieve the same and maybe have this fixed by iXSystems :)