DevOps Dictionary

Xen is an open-source, type-1 hypervisor that runs directly on bare-metal hardware to host multiple isolated virtual machines (VMs) on a single server. It addresses the challenge of securely sharing CPU, memory, storage, and networking across different workloads by inserting a thin control layer that schedules hardware access and enforces isolation so each VM behaves like an independent computer. At a high level, Xen separates guest VMs from the underlying devices and typically relies on a privileged management domain (often called Dom0) to provide device drivers and handle VM lifecycle operations such as creation, teardown, and resource allocation.

With Xen, teams can consolidate servers, improve utilization, and apply consistent isolation boundaries between tenants or services; without it, workloads often require dedicated machines or accept weaker separation, increasing cost, sprawl, and the blast radius of failures or compromise. This gap exists because the hypervisor can mediate privileged hardware operations in a way a general-purpose OS cannot reliably enforce between competing guests.