All Nutanix containers are thin provisioned by default; this is a feature of NDFS. Thin provisioning is a widely accepted technology that has been proven over time by multiple storage vendors, including VMware. As containers are presented by default as NFS datastores to VMware vSphere hosts, all VMs will also be thin provisioned by default. This results in dramatically improved storage capacity utilization without the traditional performance impact. Thick provisioning on a VMDK level is available if required for the limited use cases such as fault tolerance (FT) or highly demanding database and I/O workloads. Thick provisioning can be accomplished by creating Eager Zero Thick VMDKs. Eager Zero Thick VMDKs will automatically guarantee space reservations within NDFS.
Here is the disconnect. When I provision a lazy or eager zeroed, 1TB VM, both cause container storage utilization to jump by 2TB (replication factor of 2 is in use). I would expect to see only the eager zeroed VM to cause the jump, since lazy should be thin provisioned. Also, when I create a lazy zeroed VM, after the VM creation is complete the disk is listed as eager?
Best answer by Jon
Thick ANY causes NOS to reserve the space on the backend. The only difference is whether it zeros it out up front or not, as you know lazy vs eagar.
This is because if you are telling Nutanix you want thick, we dont want to accidently have the system run out of space, like some other storage systems do, so we'll respect that lazy reservation for you automagically.
Summary - the jump you are seeing is because we automatically reserve the space. This doesnt mean we zero it out for you, just make a reservation.
Anyhow, fun fact, win NOS 4.6, we added Zero avoidance to the write cache layer (aka oplog), so zero operations should be much faster now, because we just see the zero and update metadata, instead of writing the zero to cache. very slick and cool stuff.