PS5 will follow a similar approach to PS4's when it comes to expandable storage.
Sony has clarified how players will be able to expand the PS5 storage space. The console uses a custom-made SSD by default, and has an NVMe slot for owners to manually expand the available storage.
However, not every off-the-shelf NVMe drive will work. First, the off-the-shelf SSD needs to physically fit into the M.2 expansion slot in the PS5. Sony also needs to validate the speeds of the different models to ensure compatibility.
Unfortunately, those drives will still be slower than the internal drive, because so few of the currently available PCIe 4.0-based options can match the speed of Sony's own custom drive. There's also another problem, and it has to do with how PS5 assigns data priorities.
The internal drive has access to up to six priority levels, whereas the off-the-shelf drives can only have two. The good news is that, for older games (PS4), any USB hard drive will work. You can play those games off the drive itself, or use it for storage and move them to the SSD before playing.
This stands in stark contrast to Microsoft's solution for Xbox Series X, which has its own, proprietary slot that's easier for users to understand. Sony's idea could prove more successful in the long run, as faster drives become available - and cheaper, but it's complicated right now.
As part of his talk, lead system architect, Mark Cerny, said Sony will reveal the PS5 compatible drives and their speeds later down the line.