Glossary
General
| Acronym | Meaning | Definition |
|---|---|---|
| CPU | Central Processing Unit | Processor. |
| OS | Operating System | Software environment running on a VM or physical machine. |
Core infrastructure
| Acronym | Meaning | Definition |
|---|---|---|
| VM | Virtual Machine | A guest machine (OS + virtual hardware) managed by the pool. |
| SR | Storage Repository | A storage container (local LVM, NFS, iSCSI, etc.) where VDIs live. |
| VDI | Virtual Disk Image | A virtual disk object on an SR (root disk, data disk, ISO, snapshot disk, etc.). Not to be confused with Virtual Desktop Infrastructure. |
| VBD | Virtual Block Device | The attachment that connects a VDI to a VM (device number, bootable flag, mode). |
| VIF | Virtual Network Interface | A virtual NIC on a VM, connected to a network. |
| PIF | Physical Interface | A physical NIC on a host, used for management, storage, or guest networks. |
| PBD | Physical Block Device | Binds an SR to a host (how the host reaches that storage). |
| Host | — | A hypervisor server (XCP-ng / XenServer node) in the pool. |
| Pool | — | A set of hosts sharing storage and network configuration. |
Virtualization modes & hardware
| Acronym | Meaning | Definition |
|---|---|---|
| HVM | Hardware Virtual Machine | Full hardware-emulated guest (typical for Windows and many Linux installs). |
| PV / PVM | Paravirtualization | Guest uses paravirtualized drivers/interfaces (legacy Linux style on Xen). |
| vCPU | Virtual CPU | A virtual processor presented to the VM. |
| GPU | Graphics Processing Unit | Physical graphics hardware on a host. |
| vGPU | Virtual GPU | A virtual GPU slice assigned to a VM. |
| PGPU | Physical GPU | A physical GPU as seen by XAPI (grouping / passthrough context). |
| VTPM | Virtual Trusted Platform Module | Software TPM device exposed to a VM (e.g. Windows 11 / BitLocker). |
Networking & storage
| Acronym | Meaning | Definition |
|---|---|---|
| MTU | Maximum Transmission Unit | Largest Ethernet payload size on a link (e.g. jumbo frames). |
| VLAN | Virtual LAN | Logical LAN segment; often tied to PIF tagging in XAPI. |
| SR-IOV | Single Root I/O Virtualization | Passing a virtual function of a physical NIC to a VM for near-native I/O. |
| NFS | Network File System | File-based SR backed by an NFS export. |
| iSCSI | Internet Small Computer System Interface | Block SR backed by an iSCSI LUN. |
| LVM | Logical Volume Manager | Local volume–style SR (e.g. on host disks). |
| ISO SR | ISO Storage | SR type used to store .iso images for VM install media. |
High availability & resilience
| Acronym | Meaning | Definition |
|---|---|---|
| HA | High Availability | Pool feature to restart VMs elsewhere if a host fails (policy-driven). |
XCP-ng/Xen Orchestra-specific
| Acronym | Meaning | Definition |
|---|---|---|
| XO | Xen Orchestra | The management UI/API stack (xo-server, xo-web, etc.). |
| XOA | Xen Orchestra Appliance | Prebuilt VM image that runs XO as a packaged appliance. |
| XAPI / xapi | Xen API | The management API and service on each host that XO talks to. |