Western Digital purple surveillance hard drive is really popular for recording video.
Security Camera are trending towards 4K Cameras and 4K NVR, hence there is a huge demand for inexpensive affordable storage.
Most commonly used now is the 4 TB because of the value and 8 TB is also excellent for 4K NVR. Please check compatibility of 8TB or 10TB hard drive before purchase, older DVR and NVR might not be compatibly with them.
Please refer to this article from manufacturer for more information