Here's how scalable storage works on PS5

For scalable storage, the PS5 will take a similar approach to the PS4.

Sony has clarified how players will expand PS5 storage space. The console uses a custom SSD by default and has NVMe slots for owners to manually expand available storage.

However, not every ready-made NVMe drive can be used. First, off-the-shelf SSDs need to be physically suitable for M.2 expansion slots in PS5. Sony also needs to verify the speed of different models to ensure compatibility.

Unfortunately, these drives will still be slower than the built-in drives, as few PCIe 4.0-based options currently compare to Sony's own custom drives. There is another issue related to how the PS5 assigns data priority.

Internal drives can access up to six priorities, while off-the-shelf drives can only have two priorities. The good news is that for older games (PS4), any USB hard drive will work. You can play these games on the drive itself, or you can use them for storage and then move them to SSD before playing.

This is in stark contrast to Microsoft's Xbox Series X solution, which has its own proprietary slot for users to understand. In the long run, with the introduction of faster drives and cheaper prices, Sony's idea may be more successful, but now this is complicated.

Chief System Architect Mark Cerny said in a speech that Sony will release PS5-compatible drives and their speeds later.