In virtual storage, thick provisioning is a type of storage allocation in which the amount of storage capacity on a disk is pre-allocated on physical storage at the time the disk is created.
This means that creating a 100GB virtual disk actually consumes 100GB of physical disk space, which also means that the physical storage is unavailable for anything else, even if no data has been written to the disk.
Thick provisioning contrasts with thin provisioning, which provisions storage on an as-needed basis. Thin provisioning helps to avoid wasted physical capacity and can save businesses on up-front storage costs. However, thick provisioning has the benefit of less latency because all storage is allocated at once when virtual machines are created.