[one-users] qcow2: empty datablock image creation with preallocation

[Lorenzo Faleschini]

Hi

is it possible to create in sunstone (or via CLI) an empty-datablock 
qcow2 with preallocation (-o preallocation=metadata).

I need it to avoid the auto-grow overhead.

for now I create the prealloc qcow2 image then I import it in one.

is it posible to avoid this step?
any suggestions or alternatives?

thanks

Lorenzo