The storage needed varies to the recording image. It is recommended to test directly. Suppose 640x480 is selected with 3fps, each channel needs 6.2G storage space every day for recording. A total of 24.8G will be needed for 4-channel recording. If using QNAP NAS-4300 that supports 2T storage (250G HDD x 8), about 8 VioGate servers of 32-channel recording can be supported for 10-day recording.
When using 320x240, you can count the amount by one fourth of 640x480.