Which statement about thick provisioning is true?

• A. Thick provisioning allocates capacity on demand.
• B. Thick provisioning reallocates space dynamically.
• C. Thick provisioning reduces I/O performance.
• D. Thick provisioning reserves fixed capacity upfront.

Answer: (D)

Thick provisioning reserves fixed capacity upfront. When a disk is created as thick-provisioned, the storage array commits the full size immediately, guaranteeing that space for that disk and preventing others from using it. This upfront reservation provides predictable space and can lead to more consistent performance because there’s no need to allocate blocks on the fly during writes. It contrasts with thin provisioning, which allocates space on demand as data is written. Thick provisioning does not reallocate space dynamically after creation. Also, it does not inherently reduce I/O performance; in many setups it can even improve consistency by removing allocation overhead during writes.