Drut's agile optical fabric for the data centre

A US start-up has developed a photonic fabric for the data centre that pulls together the hardware needed for a computational task.

Drut Technologies offers management software and a custom line card, which, when coupled with the optical switch, grabs the hardware required for the workload.

Some of the Drut team (L to R): Sumit Jayaswal, member of technical staff; Bill Koss, CEO; and Jitender Miglani, founder and president.

“You can have a server with lots of resource machines: lots of graphic processing units (GPUs) and lots of memory,” says Bill Koss, CEO of Drut. “You create a machine, attach a workload to it and run it; forever, for a day, or 15 minutes.”

Drut first showcased its technology supporting the PCI Express (PCIe) bus over photonics at server specialist, SuperMicro’s exhibition stand, at the Supercomputing 22 show held last November in Dallas, Texas.

“This is a fully reconfigurable, direct-connect optical fabric for the data centre,” says Koss.

Drut says hyperscalers use between 40 and 60 per cent of the hardware in their data centres. With direct connectivity, resources can be used as needed and released, improving overall hardware utilisation.

Optical circuit switching

Drut’s system is a second recent example of a company using optics for the data centre to establish reconfigurable photonic paths between endpoints, referred to as optical circuit switching.

Google revealed in August 2022 that it had developed its own MEMS-based optical switch design, which the hyperscaler has used for several years in its data centres.

The optical circuit switches are used instead of the highest tier of Ethernet switches - the spine layer - in Google’s data centres.

Using optical circuit switching reduces networking costs by 30 per cent and power consumption by over 40 per cent. The optical switch layer also enables more efficient and less disruptive upgrading of the server endpoints.

Koss says the difference between its design and Google’s is scale: “Ours is more granular.”

Drut says its solution will enable racks of optically-attached machines, but unlike Google, the optical switching is much closer to the end equipment. Indeed, it is a second fabric independent of the data centre’s tiered Ethernet switches.

Drut's area of focus is within the blue-lined box. Source: Drut

Product architecture

The main three elements of Drut’s technology are an FPGA-based line card, the fabric-manager software and a third-party optical switch.

Drut’s line card, the iFIC 1000, has an FPGA and four 100-gigabit transceivers. “That is as much as we can fit on,” says Koss.

The system architecture showing the iFIC cards, the optical switch, and the management software. Source: Drut

The company uses its own transport protocol that runs over the fabric, an ‘out-of-band’ network design.

“You can dynamically attach and detach, and the machine doesn’t go into crazy land,” says Koss.

The fabric manager knows all the ports of the switch and the endpoints and sets up the desired system configurations.

With the fabric management software and the FPGA, the system can configure banks of graphic processing units (GPUs).

Drut has also demonstrated linking memory over its photonic fabric, although this is in development and still unavailable as a product.

Drut says a primary challenge was developing the FPGA that takes the out-of-band signalling off the main bus and supports it over the optical fabric.

A photonic fabric design promises to change the nature of a server. A user will request CPUs, accelerators such as GPUs and FPGAs, and memory, as needed, for each workload.

The merits of using an optical switch include its support for multiple ports, i.e. the switch’s large radix, and its being interface-speed agnostic.

The photonic switch also has a lower latency than switch ICs and simplifies cabling. “It is all single-mode fibre pluggable optics,” says Koss.

Drut argues that optical switches arrived 25 years too early but that, with developments in the data centre, their timing is now right. Source: Drut.

Status

Drut is developing a second line card which will use a larger FPGA. Each card generation will expand the number of optical ports to scale the endpoints supported.

The company is also working with a co-packaged optics player on a design for a hyperscaler.

“We use pluggable optics today because co-packaged optics isn’t available,” says Koss.

The advantage of co-packaged optics is that it will increase the port density on each line card and hence the overall scaling.

Koss says that Drut already has two customers: an enterprise and a cloud provider.

Drut, which means ‘high tempo’ in Sanskrit, has so far secured two rounds of funding.

“We did a good-sized seed round in June 2021 and closed a bigger seed extension last September; not an easy task in 2022,” says Koss. “We added Boston Seed Capital and another firm as new investors as well.”

The company has sufficient funding till 2024 and is talking to new investors for a Series A funding round.