TrueNAS ISCSI Thin Provisioning to ESXi


Active Member
Jul 2, 2013
Bit confused with this, maybe someone can show me where I am making a mistake or three

I've setup a pool that consists of 4 vdev mirrors giving a pool space of 2.21TiB - got a couple of ESXi 7.0u3 servers using this pool.

I've migrated a bunch of VM's onto it. TrueNAS is reporting a pool utilisation of 21%. Fantastic, thats the sparse config and compression kicking in... except the datastore figure in vCenter is reporting 2.11TB used out of 2.21TB....

This is down to the way VMWare copy inflates thin volumes to thick as part of the copy e.g. vcenter is using about 120GB but if I used the copy command it would expand to more like 2TB since that is the max provisioned drive. So I've managed to reduce the volume size by converting the disks to thin. But I'm confused why TrueNAS isnt using VAAI to reconcile the usage.

Note I have a threshold of warning at 80% pool space utilisation, so if I take the non thin figure / non compressed figure then that makes sense

This is in the VMware logs - Space utilization on thin-provisioned device naa.6589cfc0000007de18bfaca99a20ec45 exceeded configured threshold. Affected datastores (if any): xxx - according to the VMware blurb this is coming from the storage array. But I don't see any error messages or otherwise in any TrueNAS log.

Any guidance gratefully accepted.
Last edited: