Firecracker vs KVM

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.

KVM is an open-source virtualization solution for Linux hosts with Intel VT or AMD-V extensions. It runs multiple virtual machines using unmodified Linux or Windows images, each with virtualized hardware such as a network card, disk, and graphics adapter. The documented capabilities include live migration, nested guests, CPU and PCI hotplug, virtio devices, and device assignment; snapshots and GPU acceleration are also listed. KVM’s kernel component is part of mainline Linux, while its userspace component is part of mainline QEMU. Linux distributions commonly package the required modules and tools, and Windows guest drivers are available separately. Documented processor coverage includes Intel, AMD, ARM, PowerPC, and 64-bit S390 systems. KVM can be used with upper layers including QEMU, libvirt, OpenStack, and oVirt. It is available for Linux and self-hosted use, and the listed plan is free. The host must have Intel VT or AMD-V virtualization extensions.