Kioxia Optical Interface SSD Demoed at FMS 2024 - ServeTheHome

Kioxia has something new and very cool coming. At FMS 2024, the company is showing off a SSD with an optical interface. This is one where hopefully Patrick, George, or Virginia will snap a few photos later this week, but here are the details before the show floor opens.

Note: We updated this with photos from the show floor.

Kioxia is developing an optical interconnect SSD for PCIe Gen8 or later, but is starting to show the technology now.

The current demo is a very short range 40m in distance (~131ft) optical connection, but the company plans to have 100m distance in the future. One of the concepts is that this could allow for SSDs to be placed in locations far away from hot CPUs and GPUs that may be liquid-cooled. Instead, NAND can be placed in a more moderate temperature room or containment area where it performs the best.

Another idea is that this could be a smaller connector, but we are not sure about this one. A standard MTP/MPO connector is smaller (although we are not sure that is what is being shown since it looks a bit different), but it does not provide power.

Update: Here is the demo running. The SSD connects to a board that converts PCIe signaling to optical signaling.

We asked, and in theory this type of technology can be used for things like GPUs.

We asked and this demo is more like PCIe over optics (without the electrical part) rather than converting it into another protocol like Ethernet.

Another advantage is that it can be switched using optics. To us, this is the big winner, with some caveats. In theory, even using 100m SR optics, one could then use switches to aggregate bandwidth, share devices, and extend the distance between SSDs and host servers.

At some point, the question will be how this is done. Currently, optical networking is so much faster than SSDs and increasing at a faster rate that perhaps the option is to use switches to add SSDs to networks, either PCIe, CXL, or Ethernet-based. For some sense of scale, PCIe Gen5 NVMe SSDs are just being rolled out by all major SSD vendors (Kioxia has had PCIe Gen5 NVMe SSDs for some time.) At the same time, it would take around 16 top-end PCIe Gen5 x4 SSDs to fill a single 800GbE port on the Marvell Teralynx 10 51.2T Switch we just reviewed.

At some point with networking like this, the question will be whether we should directly attach SSDs using optical interconnects or if SSDs will move to switches that are then optically connected.

This feels like the next frontier of Ethernet SSDs like the older Kioxia EM6 NVMeoF SSD. Although Kioxia has not said if the optical interface SSDs will be Ethernet, PCIe, or CXL-based, at some point the major problem is sharing enough storage with systems in a manner that makes sense. Another opportunity is to share pools of SSDs among larger clusters, especially as we move to an era of CXL 2.0, CXL 3.1, and beyond switches.

If you want to see what feels like a “granddaddy” technology, you can check out the Kioxia EM6 video above. It was a way to solve a similar challenge using older technology.