hard drive – Connect SATA storage device to 2 computers at a time

There is an IP camera NVR (a box that has a SATA HDD 3,5″ in it and records the cameras video to the HDD).

But I don’t have access to the “NVR as root”.

Question: How can I (while the NVR is using the HDD in RW mode) reach the HDD in a read-only mode? ex.: A rbpi can do it?