We're talking mastering here. For editing it doesn't matter since it can and is done in proxies. Depending on the bit-depth and fps we're talking anywhere between ~127 MBps to ~253MBps (1+ - 2+ Gbps) per workstation. Usually there are several and a one heavy NAS or several smaller ones. That's for 2K (and HD - but then it's a bit smaller bandwidth). For 4K it's four times that.