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XenServer

Enterprise Resource Center • Virtualization Knowledge Base

Understanding XenServer

XenServer is a server virtualization platform that runs directly on physical server hardware and allows multiple virtual machines to share CPU, memory, storage and networking resources. XenServer hosts can be managed individually or combined into pools for centralized administration, shared storage and workload mobility.

XenServer XenCenter Virtual Machines Host Pools Hypervisor
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Quick Answer

What Is XenServer?

XenServer is a server virtualization platform that installs directly on compatible physical hardware and hosts multiple virtual machines. Each VM can receive virtual CPU, memory, disks and network interfaces while running its own operating system and applications.

XenServer environments can be administered through XenCenter or command-line and API-based management tools. Multiple hosts can also be grouped into pools to simplify centralized management and enable features such as shared storage and VM migration.

Virtualization Architecture

Physical Server → XenServer → Virtual Machines

XenServer abstracts physical compute resources and presents them to virtual machines as software-defined hardware.

LAYER 1

Physical Hardware

CPUs, memory, storage controllers, disks and network adapters provide the physical resources.

LAYER 2

XenServer

XenServer runs directly on the host and manages the virtualization environment and access to physical resources.

LAYER 3

Virtual Machines

Software-defined computers receive virtual CPU, memory, disks and networking.

LAYER 4

Guest Operating Systems

Supported Windows and Linux operating systems run inside the virtual machines.

XenServer Fundamentals

Core XenServer Components

XenServer Host A physical server running XenServer and providing resources to virtual machines.
Virtual Machines Software-defined systems with their own operating system, virtual CPU, memory, disks and NICs.
XenCenter Windows-based graphical management software for XenServer hosts, pools, storage and virtual machines.
Host Pool Multiple XenServer hosts can be combined into a centrally managed pool.
Management

What Is XenCenter?

XenCenter is the graphical Windows-based management interface for XenServer. Administrators can use it to connect to hosts and pools, deploy virtual machines, configure storage, monitor workloads and manage virtual infrastructure.

Host Management Connect to and administer XenServer hosts.
VM Management Create, configure, start, stop and monitor virtual machines.
Pool Management Manage groups of XenServer hosts as a single pool.
Storage Management Configure and monitor storage repositories used by VMs.
Multi-Host Infrastructure

XenServer Host Pools

Multiple XenServer hosts can be joined into a pool so they can be administered as one logical environment.

Centralized Management Hosts and VMs can be managed together instead of as completely independent systems.
Shared Storage Pool members can use shared storage repositories when the infrastructure is configured appropriately.
VM Migration Supported configurations can move running VMs between hosts with live migration.
Availability Pool-level features can support higher-availability designs when infrastructure requirements are met.
Virtual Machine Storage

XenServer Storage Repositories

XenServer organizes virtual machine storage through storage repositories, commonly abbreviated as SRs. A storage repository provides the container in which virtual disks are stored.

Local Storage Storage installed directly in an individual host can provide local VM capacity.
Shared Storage Shared repositories can be made accessible to multiple hosts in a pool.
Storage Performance Latency, IOPS and throughput affect virtual-machine responsiveness.
Redundancy Storage redundancy should be designed independently according to workload and availability requirements.
Compute Resources

XenServer CPU Considerations

XenServer schedules virtual CPU workloads across the physical processors installed in the host. Processor core count, frequency, architecture and NUMA topology can therefore affect consolidation density and virtual-machine performance.

Physical Cores Core count contributes to the host's aggregate compute capacity.
vCPUs Virtual CPUs are allocated to VMs according to workload requirements.
NUMA NUMA architecture can affect memory locality and performance on multi-socket hosts. NUMA Guide → Xeon vs EPYC Compare major enterprise processor platforms used for virtualization. Compare Processors →
Memory

XenServer Memory Planning

Virtual machine density is often closely tied to physical memory capacity because every active workload requires RAM in addition to memory used by the virtualization platform.

Storage Performance

Storage Matters in Virtualized Environments

Multiple XenServer virtual machines can issue storage requests simultaneously. Storage latency, IOPS, throughput and redundancy therefore affect overall VM responsiveness and consolidation density.

Networking

XenServer Networking

Virtual machine traffic, host management, shared storage, migrations and backup operations can all consume network bandwidth in a XenServer environment.

Guest Integration

XenServer VM Tools

XenServer VM Tools provide guest integration components and optimized drivers for supported virtual machines. Appropriate guest tools and paravirtualized drivers can improve storage and network performance and provide better interaction between the guest operating system and XenServer.

Storage Drivers Optimized drivers can improve virtual disk I/O efficiency.
Network Drivers Paravirtualized network drivers improve virtual NIC performance.
Guest Integration Tools provide additional communication between the guest and virtualization platform.
Performance XenServer recommends VM Tools for optimal supported guest performance.
Important

XenServer Hardware Compatibility Matters

A component being physically compatible with a server does not automatically make it suitable for a XenServer deployment. Processor support, firmware, storage controllers, network adapters and other hardware should be validated against the XenServer release being deployed.

XenServer maintains a hardware compatibility list for supported infrastructure, and production changes should be validated against both server-vendor and XenServer requirements.

Current Platform

XenServer 9

XenServer 9 is the current major XenServer release. The platform continues to support server and desktop virtualization workloads and includes modern capabilities for host security, NUMA-aware workload placement and hardware lifecycle management.

Virtualization Consolidate multiple VMs onto compatible physical hosts.
NUMA Optimization Modern releases include NUMA-aware performance optimizations.
Host Secure Boot Supported configurations can strengthen the host boot security chain.
XenCenter Current XenCenter releases provide graphical management for supported XenServer environments.
Architecture Comparison

Physical Servers vs XenServer VMs

PHYSICAL SERVER
Dedicated Hardware Operating systems and applications consume the resources of an individual physical server directly.
XENSERVER HOST
Multiple Virtual Machines Multiple operating environments share host CPU, memory, storage and networking through virtualization.
Frequently Asked Questions

XenServer FAQ

What is XenServer?

XenServer is a virtualization platform that runs directly on physical server hardware and hosts virtual machines.

Is XenServer a hypervisor?

XenServer is a complete server virtualization platform built around the Xen hypervisor architecture.

What is XenCenter?

XenCenter is a Windows-based graphical management interface used to administer XenServer hosts, pools and virtual machines.

What is a XenServer pool?

A pool combines multiple XenServer hosts into a single managed environment.

What is a XenServer storage repository?

A storage repository is a storage container used to hold virtual disks for XenServer virtual machines.

Can XenServer run Windows and Linux VMs?

Yes. XenServer supports compatible Windows and Linux guest operating systems.

Can XenServer migrate running virtual machines?

Supported pooled configurations can live-migrate running virtual machines between XenServer hosts.

Does XenServer support non-Citrix workloads?

Yes. XenServer supports non-Citrix workloads in addition to environments integrated with Citrix products.

Enterprise Virtualization Hardware

Building or Upgrading a XenServer Host?

Tech Supply Direct can help identify compatible enterprise processors, server memory, storage, network adapters and other hardware for XenServer virtualization environments based on your platform and configuration requirements.