What about PCIe cards?
Another option is to pack as much flash as possible onto a PCIe card to sit in a high speed slot on a server. Because of their much higher interface speeds, PCIe cards have much better performance than your typical commodity SSD, but face their own unique issues. To speak with the Operating System (OS) PCIe cards require specialized software drivers. With some cards these drivers are so heavy-weight that their vendors don't even call them drivers anymore but try to convince you they are a great value added software layer. That might be true except for the fact that those cards gain their performance by stealing CPU cycles from the core that’s hosting it, the same core running the business software your trying to accelerate.