Mesosphere announced a $73.5 million C round today, including investments from Microsoft and Hewlett Packard Enterprise (HPE).

Also participating were previous Mesosphere investors Andreessen Horowitz, Khosla Ventures, and Fuel Capital, as well as new investors A Capital and Triangle Peak Partners.

The series C round brings total funding to $126 million.

“In both cases — with HPE and Microsoft — we have a business relationship in addition to financing,” says Matt Trifiro, chief marketing officer of Mesosphere.

The three-year-old company only launched its primary product — its Data Center Operating System (DCOS) — in 2014 and already counts Verizon and Apple among its customers. The core of DCOS is the open source Apache Mesos kernel.

Trifiro says this round with Microsoft and HPE “represents a significant realignment of the industry around the transformation of the data center.”

For Microsoft, Mesosphere is bringing its DCOS to Windows servers. “Windows is the largest server-based OS in world,” says Trifiro. “This will allow an operator to treat both Linux and Windows as if they were one big pool of resources.”

Mesosphere isn’t saying what kind of customer relationship it has with HPE, but Lak Ananth, managing director at Hewlett Packard Ventures, said in the funding announcement, “Mesosphere’s DCOS is the most exciting new enterprise operating system since Linux.”

Mesosphere also announced the version 1.0 release of its Marathon container orchestrator for its DCOS.

Marathon competes with Google’s Kubernetes. However, Trifiro says, Kubernetes runs on the DCOS and is one of a few options that compete with Marathon. “We have a partnership with Google and CNCF — the stewards of Kubernetes."

Microsoft uses DCOS in the Azure cloud. Enterprises prefer Mesosphere's orchestration for its maturity, said Scott Guthrie, Microsoft's executive vice president of cloud and enterprise, in today's press release.

The open source Marathon 1.0 includes new features around networking and security.

Finally, Mesosphere introduced its Velocity platform for improving developer agility via continuous integration and continuous deployment (CI/CD) with DCOS. Velocity helps developers who are already running CI/CD environments built on Mesos, Jenkins, Docker, and other tools.