Special allocation classes sizing

[Pascal Guitierrez]

Hi there,

We are looking at migrating a rather large existing pool of around 400TB
onto a new pool, taking advantage of the special allocation classes in
12.2-RELEASE (just using the default special, not dedup or small_blocks).

I am about to procure the hardware needed, however I’m not sure how big to
make the special storage layer.

Is there a rough estimate calculation or perhaps I can run zdb on the
existing pool to get an estimate?

Thanks for your time