Which statement contrasts thin and thick provisioning?

• A. Thin provisioning allocates capacity upfront.
• B. Thin provisioning allocates capacity on demand; thick provisioning reserves fixed capacity upfront.
• C. Thin provisioning allocates capacity on demand; thick provisioning allocates capacity on demand.
• D. Thick provisioning allocates capacity on demand; thin provisioning reserves fixed capacity upfront.

Answer: (B)

Thin provisioning allocates capacity on demand from a shared pool, meaning space is only committed as data is written. Thick provisioning reserves a fixed amount of space upfront, guaranteeing that exact amount is set aside for the volume regardless of current usage. The best statement captures this contrast by saying thin provisioning uses on-demand allocation while thick provisioning reserves upfront capacity. This mirrors how storage pools are managed: thin maximizes utilization by not wasting space, but can lead to overcommitment; thick provides predictable availability and performance because the space is reserved in advance. The other options misstate one or both mechanisms—either claiming thin allocates upfront, or claiming both approaches allocate on demand, or attributing on-demand to thick provisioning.