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Glossary

All terms and acronyms used throughout this documentation, with links to the pages covering them.

  • Bond: aggregation of several physical NICs into one logical interface, for redundancy and bandwidth. See bonds.
  • Coalesce: background process merging a disk chain after snapshot deletion, reclaiming space. See coalesce.
  • DMC (Dynamic Memory Control): lets a VM's memory vary between a min and a max while it runs. See dynamic memory.
  • dom0 ("Domain 0", or "control domain"): the privileged Linux system started by Xen at boot. It has direct access to hardware, runs the toolstack and the storage/network backends for all VMs. See architecture.
  • domU: any unprivileged Xen domain, i.e. a regular VM (by opposition to dom0).
  • DRBD: replicated block device technology used by XOSTOR/LINSTOR. See XOSTOR.
  • Guest tools: PV drivers plus a management agent installed inside the guest OS, required for good performance and features like clean shutdown or IP reporting. See guest tools.
  • HA (High Availability): pool feature restarting protected VMs automatically when a host fails. See high availability.
  • HVM (Hardware Virtual Machine): VM mode using CPU virtualization extensions; the standard mode for all guests on XCP-ng (usually with PV drivers on top, aka "PVHVM").
  • IQN (iSCSI Qualified Name): the identifier of an iSCSI initiator or target, e.g. iqn.2024-01.com.example:storage1.
  • LINSTOR: the software-defined storage orchestrator behind XOSTOR. See XOSTOR.
  • LUN (Logical Unit Number): a block device exported by a SAN over iSCSI, Fibre Channel or SAS.
  • MTU (Maximum Transmission Unit): the largest packet size on a network; 1500 by default, up to 9000+ for jumbo frames. See MTUs.
  • NBD (Network Block Device): protocol exposing a disk over the network; used by Xen Orchestra for faster backups (see NBD backup network).
  • OVA / OVF (Open Virtualization Archive/Format): vendor-neutral VM interchange format, used to exchange VMs with non-XCP-ng platforms. See import and export.
  • OVS (Open vSwitch): the virtual switch used by XCP-ng to connect VIFs, PIFs, VLANs and tunnels. See network architecture.
  • PBD (Physical Block Device): the XAPI object connecting one host to one SR. See SR management.
  • PIF (Physical InterFace): the XAPI object representing a host network interface (a NIC, a bond or a VLAN on them).
  • Pool (resource pool): a group of hosts managed as one entity, sharing configuration and (usually) storage. See hosts and pools.
  • Pool coordinator (formerly "pool master"): the pool member exposing the XAPI endpoint for the whole pool and holding the reference database.
  • PV (ParaVirtualization): historical VM mode without hardware virtualization extensions; removed on modern XCP-ng. "PV drivers" survived: they're the efficient drivers guests use to talk to dom0.
  • QCOW2: virtual disk format available from XCP-ng 8.3, enabling disks larger than 2 TiB. See the QCOW2 FAQ.
  • RPU (Rolling Pool Update): updating a whole pool without VM downtime, orchestrated by Xen Orchestra. See updates.
  • RRD (Round-Robin Database): fixed-size database in which hosts record their performance metrics. See monitoring.
  • SMAPI: the Storage Manager API, the layer of drivers implementing each SR type.
  • Snapshot: point-in-time capture of a VM's disks (optionally with its RAM). See snapshots.
  • SR (Storage Repository): a storage target holding virtual disks (or ISOs). See storage.
  • Template: blueprint used to create VMs, with or without disk content. See templates.
  • vApp (VM appliance): a group of VMs started and recovered together, with a defined boot order.
  • VBD (Virtual Block Device): the XAPI object connecting a VDI to a VM.
  • VDI (Virtual Disk Image): one virtual disk, stored in an SR.
  • VHD: the historical copy-on-write virtual disk format of XCP-ng (2 TiB limit per disk).
  • VIF (Virtual InterFace): a VM's virtual network card, connected to a network.
  • VLAN: layer-2 network segmentation (802.1Q tags); XCP-ng networks can sit on any VLAN. See VLANs.
  • VM (Virtual Machine): you probably know this one.
  • vTPM: virtual TPM 2.0 device, available from XCP-ng 8.3 (needed for Windows 11). See advanced VM settings.
  • XAPI: the toolstack (API and daemon) managing XCP-ng hosts and pools. See XCP-ng API.
  • XCP (Xen Cloud Platform): the historical open source distribution of XenServer, ancestor of XCP-ng ("XCP new generation").
  • xe: the command-line client for XAPI, available on every host. See the xe CLI page and the full command reference.
  • Xen: the type-1 hypervisor XCP-ng is built on.
  • XO / XOA (Xen Orchestra / XO Appliance): the web-based management, backup and orchestration platform for XCP-ng; XOA is its turnkey virtual appliance form. See manage at scale.
  • XOSTOR: XCP-ng's hyperconverged storage (replicated storage built from the hosts' local disks). See XOSTOR.
  • xsconsole: the text-mode configuration console displayed on a host's physical/serial screen.
  • XVA: the native file format for exported VMs and templates. See import and export.