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Is this thing on? Using OpenBMC and ACPI power states for reliable server boot

At Cloudflare, we provide a range of services through our global network of servers, located in 330 cities worldwide. When you interact with our long-standing application services, or newer services like Workers AI, you’re in contact with one of our fleet of thousands of servers which support those services.

These servers which provide Cloudflare services are managed by a Baseboard Management Controller (BMC). The BMC is a special purpose processor  — different from the Central Processing Unit (CPU) of a server — whose sole purpose is ensuring a smooth operation of the server.

Regardless of the server vendor, each server has this BMC. The BMC runs independently of the CPU and has its own embedded operating system, usually referred to as firmware. At Cloudflare, we customize and deploy a server-specific version of the BMC firmware. The BMC firmware we deploy at Cloudflare is based on the Linux Foundation Project for BMCs, OpenBMC. OpenBMC is an open-sourced firmware stack designed to work across a variety of systems including enterprise, telco, and cloud-scale data centers. The open-source nature of OpenBMC gives us greater flexibility and ownership of this critical server subsystem, instead of the closed nature of proprietary firmware. Continue reading