DevOps Dictionary

Xen is an open-source type-1 hypervisor, meaning it runs directly on server hardware to host multiple isolated virtual machines (VMs) on the same physical system. It addresses the need to safely share compute resources across workloads by abstracting CPU, memory, storage, and networking so each VM behaves like its own server. At a high level, Xen schedules hardware resources between VMs and enforces isolation, typically using a small, privileged management domain (often called Dom0) to handle device drivers and VM lifecycle operations while guest VMs run their operating systems independently.

With Xen, teams can consolidate servers, improve utilization, and apply consistent controls for isolation and failover; without it, workloads often require dedicated machines or weaker isolation, increasing cost, operational sprawl, and the blast radius of misconfiguration or compromise. This gap exists because the hypervisor layer can partition and mediate access to hardware in a way general-purpose operating systems alone cannot reliably enforce across competing workloads.