Firecracker vs QEMU

Firecracker is open-source virtualization software for running container and function workloads in lightweight microVMs. It uses Linux KVM hardware virtualization to isolate each workload and exposes only five emulated devices, a design intended to reduce attack surface. MicroVMs start in under 125 ms, add under 5 MiB of memory overhead each, and a host can create up to 150 per second while packing thousands onto one server. A RESTful API configures and starts the VMs, while rate limiters govern network and storage bandwidth and operations. The companion jailer adds Linux user-space security barriers. Firecracker supports Linux hosts and guests with kernel versions 4.14 and above, plus OSv guests, on production 64-bit Intel, AMD, and Arm CPUs with hardware virtualization. VM snapshots are supported, but GPU acceleration is not. It is free under Apache 2.0, with integrations including containerd, Kata Containers, and Fly.io.

QEMU is a free, open-source machine emulator and virtualizer. System emulation models an entire machine, including its CPU, memory and devices, so it can run a guest operating system. User-mode emulation runs processes built for one CPU architecture on another. The package also includes qemu-img, a command-line utility for creating, converting and modifying disk images. QEMU can work with KVM, Xen and Hypervisor.Framework so guests can run directly on the host CPU. Supported build platforms include Linux, macOS, FreeBSD, NetBSD, OpenBSD and Windows. Windows support is limited to 64-bit, while macOS requires the newest version currently available; support for the prior version is eventually dropped. For complex networking and storage configurations, the project recommends management tools such as virt-manager. Its security guidance distinguishes virtualization with an accelerator and listed machine type from TCG non-virtualization use, which does not provide guest-isolation or security guarantees. QEMU is released under GNU GPL version 2, with some components under specific licenses.