Home > APEX > Storage > White Papers > Dell APEX Block Storage for AWS > Thin provisioning
Capacity is “on reserve,” and not allocated until used. This policy enables more flexibility in provisioning. Whereas thick capacity is limited to available capacity, thin capacity provisioning can be oversubscribed, as follows:
Maximum thin capacity provisioning = 5 * (gross capacity - used capacity)
When capacity usage reaches the level where it can cause IO errors, alerts are generated. At certain higher capacity levels, volumes (even thin volumes) can no longer be created.
Consequently, thick provisioning capacity is allocated immediately, even if not actually used. Thick capacity is limited to available capacity.