Both PlayStation 5 models feature a custom 825 GB SSD of which 667 GB are available for game installation. At first that will have to be enough as storage expansion will not be enabled at launch – instead this feature is “reserved for a future update”. The PS5 has a standard M.2 slot for SSDs, however only the latest PCIe 4.0 drives will be fast enough to match the console’s internal SSD (they need to hit 5.5 GB/s, which is faster than a PCIe 3.0 x4 bus can manage). And that’s not the only requirement either. Mark Cerny, the lead designer of the console, told The Verge that drives need...
Source: https://www.gsmarena.com/playstation_5s_expandable_storage_will_not_be_enabled_at_launch-news-46174.php
