Technical FAQs
Hardware
What are the minimum system requirements for running XenServer?
For the minimum system requirements for this release, see System requirements.
Do I need a system with a 64-bit x86 processor to run XenServer?
Yes. Either an Intel VT or AMD-V 64-bit x86-based system with one or more CPUs is required to run all supported guest operating systems.
For more information about host system requirements, see System requirements.
Do I need a system with hardware virtualization support?
You need a 64-bit x86 processor-based system that supports either Intel VT or AMD-V hardware virtualization technology in the processor and system firmware.
What systems are certified to run XenServer?
For a complete list of XenServer certified systems, see the Hardware Compatibility List (HCL).
Does XenServer support AMD Rapid Virtualization Indexing and Intel Extended Page Tables?
Yes. XenServer supports AMD Rapid Virtualization Indexing and Intel Extended Page Tables. Rapid Virtualization Indexing provides an implementation of nested tables technology used to further enhance the performance of the Xen hypervisor. Extended Page Tables provide an implementation of hardware-assisted paging used to further enhance the performance of the Xen hypervisor.
Can XenServer run on a notebook or desktop-class systems?
XenServer runs on many notebook or desktop-class systems that conform to the minimum CPU requirements. However, XenServer only supports systems that have been certified and listed on the Hardware Compatibility List (HCL).
You can choose to run on unsupported systems for demonstration and testing purposes. However, some features, such as power management capabilities, do not work.
Can XenServer be installed on SD or USB cards?
No. XenServer does not support using SD cards or USB cards for your XenServer installation.
We only support hardware that has been certified and listed on the Hardware Compatibility List (HCL).
Product limits
Note:
For a complete list of XenServer supported limits, see Configuration Limits.
What is the maximum size of memory that XenServer can use on a host system?
XenServer host systems can use up to 6 TB of physical memory.
How many processors can XenServer use?
XenServer supports up to 448 logical processors per host. The maximum number of logical processors supported differs by CPU.
For more information, see the Hardware Compatibility List (HCL).
How many virtual machines can run on XenServer concurrently?
The maximum number of virtual machines (VMs) supported to run on a XenServer host is 1000. For systems running more than 500 VMs, we recommend allocating at least 16 GB of RAM to dom0. For more information, see Change the amount of memory allocated to the control domain.
For any particular system, the number of VMs that can run concurrently and with acceptable performance depends on the available resources and the VM workload. XenServer automatically scales the amount of memory allocated to the control domain (dom0) based on the physical memory available.
Note:
If there are more than 50 VMs per host and the host physical memory is less than 48 GB, it might be advisable to override this setting. For more information, see Memory usage.
How many physical network interfaces does XenServer support?
XenServer supports up to 16 physical NIC ports. These NICs can be bonded to create up to 8 logical network bonds. Each bond can include up to 4 NICs.
How many virtual processors (vCPUs) can XenServer allocate to a VM?
XenServer supports up to 32 vCPUs per VM. The number of vCPUs that can be supported varies by the guest operating system.
Note:
Consult your guest OS documentation to ensure that you do not exceed the supported limits.
How much memory can XenServer allocate to a VM?
XenServer supports up to 1.5 TB per guest. The amount of memory that can be supported varies by the guest operating system.
Note:
The maximum amount of physical memory addressable by your operating system varies. Setting the memory to a level greater than the operating system supported limit can lead to performance issues within your guest.
How many virtual disk images (VDIs) can XenServer allocate to a VM?
XenServer can allocate up to 255 VDIs including a virtual DVD-ROM device per VM.
Note:
The maximum number of VDIs supported depends on the guest operating system. Consult your guest OS documentation to ensure that you do not exceed the supported limits.
How many virtual network interfaces can XenServer allocate to a VM?
XenServer can allocate up to 7 virtual NICs per VM. The number of virtual NICs that can be supported varies by the guest operating system.
Resource sharing
How are processing resources split between VMs?
XenServer splits processing resources between vCPUs using a fair-share balancing algorithm. This algorithm ensures that all VMs get their share of the processing resources of the system.
How does XenServer choose which physical processors it allocates to the VM?
XenServer doesn’t statically allocate physical processors to any specific VM. Instead, XenServer dynamically allocates, depending on load, any available logical processors to the VM. This dynamic allocation ensures that processor cycles are used efficiently because the VM can run wherever there is spare capacity.
How are disk I/O resources split between the VMs?
XenServer uses a fair-share resource split for disk I/O resources between VMs. You can also provide a VM higher or lower priority access to disk I/O resources.
How are network I/O resources split between the VMs?
XenServer uses a fair-share resource split for network I/O resources between the VMs. You can also control the rate of outgoing data by using the Open vSwitch. For more information, see Control the rate of outgoing data (QoS).
Guest operating systems
Can XenServer run 32-bit operating systems as guests?
Yes. For more information, see Supported guest operating systems.
Can XenServer run 64-bit operating systems as guests?
Yes. For more information, see Supported guest operating systems.
Which versions of Microsoft Windows can run as guests on XenServer?
For a list of supported Windows guest operating systems, see Supported guest operating systems.
Which versions of Linux can run as guests on XenServer?
For a list of supported Linux guest operating systems, see Supported guest operating systems.
Can I run different versions of the supported operating systems or other unlisted operating systems?
We only support operating systems (OS) under OS vendor support. Although unsupported operating systems might continue to function, we might ask you to upgrade to a supported OS service pack before we can investigate any issues.
Applicable drivers might not be available for OS versions that are unsupported. Without the drivers, these OS versions do not function with optimized performance.
It’s often possible to install other distributions of Linux. However, XenServer can only support the operating systems listed in Supported guest operating systems. We might ask you to switch to a supported OS before issues we can investigate any issues.
Does XenServer support FreeBSD, NetBSD, or any other BSD variants as a guest operating system?
XenServer doesn’t support any BSD-based guest operating systems for general-purpose virtualization deployments. However, FreeBSD VMs running on XenServer have been certified for use in specific NetScaler products.
What are the XenServer VM Tools?
The XenServer VM Tools are software packages for Windows and Linux guest operating systems. For Windows operating systems, the XenServer VM Tools for Windows include high-performance I/O drivers (PV drivers) and the Management Agent.
For Linux operating systems, the XenServer VM Tools for Linux include a Guest Agent that provides additional information about the VM to the XenServer host.
For more information, see XenServer VM Tools.
Docker
Can I run Docker containers on my Linux VMs?
Yes. Docker is supported on Linux VMs that are hosted on XenServer.
Can I run Docker containers on my Windows VMs?
No. You cannot run Docker containers on a Windows VM that is hosted on XenServer. This restriction is because XenServer does not support nested virtualization for Windows VMs.
Does XenServer provide additional features for working with Docker?
No.
In previous releases of XenServer and Citrix Hypervisor, a Container Management supplemental pack was available that enabled you to manage your Docker containers through XenCenter. This feature has been removed.
XenCenter
For more information, see XenCenter.
Do I have to run XenCenter on a Windows computer?
Yes. The XenCenter management console runs on a Windows operating system. For information about the system requirements, see System requirements
If you don’t want to run Windows, you can manage your XenServer hosts and pools by using the xe CLI or by using xsconsole, a system configuration console.
Can I log on to XenCenter using my Active Directory user accounts?
Yes. You can set up XenCenter login requests to use Active Directory on all editions of XenServer.
For more information, see Manage users.
Can I restrict access of certain functions within XenCenter to certain users?
Yes. The Role Based Access Control feature combined with Active Directory authentication can restrict access for users in XenCenter.
For more information, see Manage users.
Can I use a single XenCenter console to connect to multiple XenServer hosts?
Yes. You can use a single XenCenter console to connect to multiple XenServer host systems.
Can I use XenCenter to connect to multiple hosts running different versions of XenServer?
Depending on the version of XenServer - yes. XenCenter is backwards-compatible with Citrix Hypervisor 8.0 and later versions. However, note that only Citrix Hypervisor 8.2 CU 1 is receiving full support.
Can I use XenCenter to connect to multiple resource pools?
Yes. You can connect to multiple resource pools from a single XenCenter console.
How can I gain access to the console of a Linux VM?
The Console tab in XenCenter provides access to the text-based and graphical consoles of VMs running Linux operating systems. Before you can connect with the graphical console of a Linux VM, install and configure a VNC server and an X display manager on the VM.
XenCenter also enables you to connect to Linux VMs over SSH by using the Open SSH Console option on the Console tab of the VM.
How can I gain access to the console of a Windows VM?
XenCenter provides access to the emulated graphics for a Windows VM. If XenCenter detects remote desktop capabilities on the VM, XenCenter provides a quick connect button to launch a built-in RDP client that connects to the VM. Or, you can connect directly to your guests by using external remote desktop software.
Command line interface (CLI)
For more information, see Command-line interface.
Does XenServer include a CLI?
Yes. All editions of XenServer include a full command line interface (CLI) – known as xe.
Can I access the xe CLI directly on the host?
Yes. You can access the CLI by connecting a screen and keyboard directly to the host, or through a terminal emulator connected to the serial port of the host.
Can I access the xe CLI from a remote system?
Yes. XenServer ships the xe CLI, which can be installed on Windows and 64-bit Linux machines to control XenServer remotely. You can also use XenCenter to access the console of the host from the Console tab.
Can I use the xe CLI using my Active Directory user accounts?
Yes. You can log in using Active Directory on all editions of XenServer.
Can I restrict access the use of certain CLI commands to certain users?
Yes. You can restrict user access on the xe CLI.
VMs
For more information, see Manage virtual machines.
Can VMs created with VMware or Hyper-V run on XenServer?
Yes. You can export and import VMs using the industry-standard OVF format.
You can also convert VMs in batches using the XenServer Conversion Manager. Third-party tools are also available.
For more information, see Conversion Manager.
What types of installation media can I use to install a guest operating system?
You can install a guest operating system by using:
- A CD in the CD-ROM drive of the host
- A virtual CD-ROM drive using technology such as DRAC
- Placing ISO images on to a shared network drive
- Network installation, if supported by the specific guest.
For more information, see Manage Virtual Machines.
Can I make a clone of an existing VM?
Yes. Any VM created on XenServer can be cloned or converted into a VM template. A VM template can then be used to create more VMs.
Can VMs be exported from one version of XenServer and moved to another?
Yes. VMs exported from older versions of XenServer can be imported to a newer version.
Can I convert a VM from the open-source version of Xen to XenServer?
No.
Does XenServer provide disk snapshot capabilities for VMs?
Yes. XenServer supports using snapshots in all editions. For more information, see VM Snapshots.
Storage
For more information, see Storage.
What types of local storage can be used with XenServer?
XenServer supports local storage such as SATA, SAS, and NVMe.
What type of SAN/NAS storage can be used with XenServer?
XenServer supports Fibre Channel, FCoE, Hardware-based iSCSI (HBA), iSCSI, NFS, and SMB storage repositories.
For more information, see Storage and the Hardware Compatibility List.
Does XenServer support software-based iSCSI?
Yes. XenServer includes a built-in software-based iSCSI initiator (open-iSCSI).
What version of NFS is required for remote storage use?
XenServer requires NFSv3 or NFSv4 over TCP for remote storage use. XenServer currently does not support NFS over User Datagram Protocol (UDP).
Can I use software-based NFS running on a general-purpose server for remote shared storage?
Yes. Although we recommend using a dedicated NAS device with NFSv3 or NFSv4 with high-speed non-volatile caching to achieve acceptable levels of I/O performance.
Can I boot a XenServer host system from an iSCSI, Fibre Channel or FCoE SAN?
Yes. XenServer supports Boot from SAN using Fibre Channel, FCoE, or iSCSI HBAs.
Can I boot a XenServer host from UEFI?
Yes. XenServer supports booting from UEFI. However, UEFI Secure Boot is not supported for XenServer hosts.
Booting from BIOS is currently supported, but is deprecated and will be removed in a future release.
For more information, see Network boot installations
Does XenServer support Multipath I/O (MPIO) for storage connections?
Yes. We recommend using multipath for resilient storage connections.
Does XenServer support a software-based RAID implementation?
No. XenServer doesn’t support software RAID.
Does XenServer support HostRAID or FakeRAID solutions?
No. XenServer doesn’t support proprietary RAID-like solutions, such as HostRAID or FakeRAID.
Does XenServer support thin cloning of existing VMs?
Yes. Thin cloning is available on local disks formatted as EXT3/EXT4, in addition to NFS and SMB storage repositories.
Does XenServer support Distributed Replicated Block Device (DRBD) storage?
No. XenServer doesn’t support DRBD.
Does XenServer support ATA over Ethernet?
No. XenServer doesn’t support ATA over Ethernet-based storage.
Networking
For more information, see Networking
Can I create private networks that isolate groups of VMs?
Yes. You can create a private network on a single host for resident VMs.
Does XenServer support multiple physical network connections?
Yes. You can connect to or associate multiple physical networks that attach to different network interfaces on the physical host system.
Can VMs connect to multiple networks?
Yes. VMs can connect to any network available to the host.
Does XenServer support IPv6?
VMs hosted on XenServer can use any combination of IPv4 and IPv6 configured addresses.
However, XenServer doesn’t support the use of IPv6 in its Control Domain (dom0). You can’t use IPv6 for the host management network or the storage network. IPv4 must be available for the XenServer host to use.
Does XenServer support VLANs on a physical network interface?
Yes. XenServer supports assigning VM networks to specified VLANs.
Do XenServer virtual networks pass all network traffic to all VMs?
By default, XenServer network interfaces are non-promiscuous and a VM can only see traffic for that VM and broadcast traffic.
This behavior can be configured depending on the network stack that you are using.
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If you are using the Linux bridge as the network stack, your virtual network interfaces can be configured for promiscuous mode. This mode enables you to see all traffic on a virtual switch. For more information about promiscuous mode configuration, see the following Knowledge Center articles:
- CTX116493 - How to Enable Promiscuous Mode on a Physical Network Card
- CTX121729 - How to Configure a Promiscuous Virtual Machine in XenServer
When you enable promiscuous mode on a virtual network interface, for a VM to make use of this configuration, you must also enable promiscuous mode within your VM.
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If you are using the Open vSwitch (OVS) as your network stack, it acts as a Layer 2 switch. A VM only sees traffic for that VM. Also, the switch-port locking in XenServer enables increased levels of isolation and security. OVS cannot be configured in promiscuous mode.
Does XenServer support bonding or teaming of physical network interfaces?
Yes. XenServer supports physical network interface bonding for failover and link aggregation with optional LACP support. For more information, see Networking.
Memory
How much memory is consumed by running XenServer?
Three components contribute to the memory footprint of a XenServer host.
- The Xen hypervisor
- The control domain on the host (dom0)
- The XenServer Crash Kernel
The amount of memory required to run dom0 is adjusted automatically. By default, XenServer allocates 1 GiB plus 5% of the total physical memory to the control domain, up to an initial maximum of 8 GiB.
Note:
The amount of memory allocated to the Control Domain can be increased beyond the default amount.
In XenCenter, the Xen field in the Memory tab reports the memory used by the Control Domain, by the Xen hypervisor itself, and by the XenServer Crash Kernel. The amount of memory used by the hypervisor is larger for hosts with more memory.
For more information, see Memory usage
Does XenServer optimize VM memory usage?
Yes. XenServer uses Dynamic Memory Control (DMC) to automatically adjust the memory of running VMs. These adjustments keep the amount of memory allocated to each VM between specified minimum and maximum memory values, guaranteeing performance and permitting greater VM density.
For more information, see VM memory.
Resource pools
For more information, see Hosts and resource pools.
What is a resource pool?
A resource pool is a set of XenServer hosts managed as a unit. Typically, a resource pool shares some amount of networked storage to allow VMs to be rapidly migrated from one host to another within the pool.
Does XenServer require a dedicated host to manage a resource pool?
No. A single host in the pool must be specified as the pool coordinator. The pool coordinator controls all administrative activities required on the pool. This design means that there is no external single point of failure. If the pool coordinator fails, other hosts in the pool continue to operate, and the resident VMs continue to run as normal. If the pool coordinator cannot come back online, XenServer promotes one of the other hosts in the pool to coordinator to regain control of the pool.
This process is automated with the High Availability feature. For more information, see High availability.
Where is the configuration data for a resource pool stored?
A copy of the configuration data is stored on every host in the resource pool. If the current pool coordinator fails, this data enables any host in the resource pool to become the new pool coordinator.
What types of configurations can be made at the resource pool level?
Shared remote storage and networking configurations can be made at the resource pool level. When a configuration is shared on the resource pool, the coordinator system automatically propagates configuration changes to all the member systems.
Are new host systems added to a resource pool automatically configured with shared settings?
Yes. Any new host systems added to a resource pool automatically receive the same configurations for shared storage and network settings.
Can I use different types of CPUs in the same XenServer resource pool?
Yes. We recommend that the same CPU type is used throughout the pool (homogeneous resource pool). However, it is possible for hosts with different CPU types to join a pool (heterogeneous), provided the CPUs are from the same vendor.
For more information, see Hosts and resource pools.
For updated information about the support for feature masking for specific CPU types, see Hardware Compatibility List.
Live Migration (formerly XenMotion)
For more information, see Migrate VMs.
Can I move a running VM from one host to another?
With live migration you can move running VMs when hosts share storage (in a pool).
Also, storage live migration allows migration between hosts that do not share storage. VMs can be migrated within or across pools.
High availability
For more information, see High availability.
Does XenServer offer high availability features?
Yes. If high availability is enabled, XenServer continually monitors the health of the hosts in a pool. If high availability detects that a host is impaired, the host is automatically shut down. This action allows for VMs to be restarted safely on an alternative healthy host.
Does XenServer high availability support local storage?
No. If you want to use high availability, shared storage is required. This shared storage enables VMs to be relocated if a host fails. However, high availability allows VMs that are stored on local storage to be marked for automatic restart when the host recovers after a reboot.
Can I use high availability to automatically sequence the restart of recovered VMs?
Yes. High availability configuration allows you to define the order that VMs are started. This capability enables VMs that depend on one another to be sequenced automatically.
Performance metrics
Do the XenServer management tools collect performance information?
Yes. XenServer provides detailed monitoring of performance metrics. These metrics include CPU, memory, disk, network, C-state/P-state information, and storage. Where appropriate, these metrics are available on a per-host and a per-VM basis. Performance metrics are available directly (exposed as Round Robin Databases), or can be accessed and viewed graphically in XenCenter or other third-party applications. For more information, see Monitor and manage your deployment.
How are XenServer performance metrics gathered?
Data for the XenServer performance metrics are collected from various sources. These sources include the Xen hypervisor, Dom0, standard Linux interfaces, and standard Windows interfaces such as WMI.
Does XenCenter display performance metrics in real time?
Yes. XenCenter displays real-time performance metrics on the Performance tab for each running VM and for the XenServer host. You can customize the metrics that are displayed.
Does XenCenter store and display historic performance metrics?
Yes. XenServer keeps performance metrics from the last year (with decreasing granularity). XenCenter provides a visualization of these metrics in real-time graphical displays.
Installation
For more information, see Install.
Does XenServer install on top of systems that are already running an existing operating system?
No. XenServer installs directly on bare-metal hardware, avoiding the complexity, overhead, and performance bottlenecks of an underlying operating system.
Can I upgrade an existing XenServer installation to a newer version?
Yes. If you are running a supported version of XenServer you can upgrade to a newer version of XenServer instead of doing a fresh installation. For more information, see Upgrade.
Can I upgrade from an out-of-support version of Citrix Hypervisor or XenServer to this version?
If your existing version of Citrix Hypervisor or XenServer is no longer in support, you cannot upgrade or update to the latest version of XenServer. Only upgrades from Citrix Hypervisor 8.2 Cumulative Update 1 are supported.
For more information, see Upgrade.
How much local storage does XenServer require for installation on the physical host system?
XenServer requires a minimum of 46 GB of local storage on the physical host system.
Can I use PXE to do a network installation of XenServer on the host system?
Yes. You can install XenServer on the host system by using PXE. You can also automatically install XenServer using PXE by creating a pre-configured answer file.
Does the Xen hypervisor run on Linux?
No. Xen is a Type 1 hypervisor that runs directly on the host hardware (“bare metal”). After the hypervisor loads, it starts the privileged management domain – the control domain (dom0), which contains a minimal Linux environment.
Where does XenServer get its device driver support?
XenServer uses the device drivers available from the Linux kernel. As a result, XenServer runs on a wide variety of hardware and storage devices. However, we recommend that you use certified device drivers.
For more information, see the Hardware Compatibility List.
Licensing
For information about XenServer licensing, see Licensing.
Technical Support
For more information about support, see Support.
Does XenServer provide direct technical support for XenServer?
Yes. For more information, visit the XenServer support pages.
Do I have to buy a XenServer technical support contract at the same time as I buy XenServer?
No. A technical support contract is included in your license purchase. For information about the level of support we provide for Premium and Standard Edition customers, visit the XenServer support pages.
What level of support does my license entitle me to?
When you buy a XenServer per-socket license, you also get the benefit of our Technical Support services. For more information about levels of support, see https://xenserver.com/support.
Can I get support if my hosts are running in Trial Edition?
If you are a Trial Edition user, you are not eligible for support. However, we value your feedback: Provide feedback.
Are there alternative channels for getting support for XenServer?
Yes. There are several alternative channels for getting technical support for XenServer. You can also use Citrix Knowledge Center or contract with authorized XenServer partners who offer technical support services.
Does XenServer provide technical support for the open-source Xen project?
No. XenServer doesn’t provide technical support for the open-source Xen project. For more information, visit http://www.xen.org/.
Can I open a technical support incident with XenServer if I’m experiencing a non-technical issue?
No. Raise any non-technical issues through Citrix Customer Service. For example, issues to do with software maintenance, licensing, administrative support, and order confirmation.