Citrix recommends using the following configuration limits as a guideline when selecting and configuring your virtual and physical environment for XenServer. Citrix fully supports for XenServer the following tested and recommended configuration limits.
Virtual machine limits
XenServer host limits
Resource pool limits
Factors such as hardware and environment can affect the limitations listed in the following tables. More information about supported hardware can be found on the Hardware Compatibility List. Consult your hardware manufacturers’ documented limits to ensure that you do not exceed the supported configuration limits for your environment.
Virtual machine (VM) limits
|Virtual CPUs per VM (Linux)||32 (see note 1)|
|Virtual CPUs per VM (Windows)||32|
|RAM per VM||1.5 TB (see note 2)|
|Virtual Disk Images (VDI) (including CD-ROM) per VM||255 (see note 3)|
|Virtual CD-ROM drives per VM||1|
|Virtual Disk Size (NFS)||2 TB minus 4 GB|
|Virtual Disk Size (LVM)||2 TB minus 4 GB|
|Virtual NICs per VM||7 (see note 4)|
Consult your guest OS documentation to ensure that you do not exceed the supported limits.
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 might lead to performance issues within your guest. Some 32-bit Windows operating systems can support more than 4 GB of RAM through use of the physical address extension (PAE) mode. The limit for 32-bit PV Virtual Machines is 64 GB. For more information, see your guest operating system Administrators Guide and Guest operating system support.
The maximum number of VDIs supported depends on the guest operating system. Consult your guest operating system documentation to ensure that you do not exceed the supported limits.
Several guest operating systems have a lower limit, other guests require installation of the XenServer Tools to achieve this limit.
XenServer host limits
|Logical processors per host||288 (see note 1)|
|Concurrent VMs per host||1000 (see note 2)|
|Concurrent protected VMs per host with HA enabled||500|
|Virtual GPU VMs per host||128 (see note 3)|
|RAM per host||5 TB (see note 4)|
|Concurrent active virtual disks per host||4096|
|Physical NICs per host||16 (See note 5)|
|Physical NICs per network bond||4|
|Virtual NICs per host||512|
|VLANs per host||800|
|Network Bonds per host||4|
|GPUs per host||12 (See note 6)|
The maximum number of logical physical processors supported differs by CPU. For more information, see the Hardware Compatibility List.
The maximum number of VMs/host supported depends on VM workload, system load, network configuration, and certain environmental factors. Citrix reserves the right to determine what specific environmental factors affect the maximum limit at which a system can function. For systems running over 500 VMs, Citrix recommends allocating 8 GB RAM to the Control Domain (Dom0). For information about configuring Dom0 memory, see CTX134951 - How to Configure dom0 Memory in XenServer 6.2 and Later.
For NVIDIA vGPU, 128 vGPU accelerated VMs per host with 4xM60 cards (4x32=128 VMs), or 2xM10 cards (2x64=128 VMs). For Intel GVT-g, 7 VMs per host with a 1,024 MB aperture size. Smaller aperture sizes can further restrict the number of GVT-g VMs supported per host. This figure might change. For the current supported limits, see the Hardware Compatibility List.
If a host has one or more 32-bit paravirtualized guests (Linux VMs), running a maximum of 128 GB RAM is supported on the host.
If you have multiple high-speed NICs, you might experience out of memory issues in dom0 during XenServer installation. If you have more than four 10Gb NICs or more than two 40Gb NICs, consider increasing the amount of dom0 memory to 8 GiB. To change the amount of dom0 memory, go to the install options in the boot menu for the XenServer host and modify the Xen boot options to include
This figure might change. For the current supported limits, see the Hardware Compatibility List.
Resource pool limits
|VMs per resource pool||4096|
|Hosts per resource pool||16|
|VLANs per resource pool||800|
|Active hosts per cross-server private network||16|
|Cross-server private networks per resource pool||16|
|Virtual NICs per cross-server private network||16|
|Cross-server private network virtual NICs per resource pool||256|
|Hosts per vSwitch controller||64|
|Virtual NICs per vSwitch controller||1024|
|VMs per vSwitch controller||1024|
|Integrated site recovery storage repositories per resource pool||8|
|Paths to a LUN||8|
|Multipathed LUNs per host||256 (See note)|
|Multipathed LUNs per host (used by storage repositories)||256 (See note)|
|VDIs per SR (NFS, SMB, EXT, GFS2)||20000|
|VDIs per SR (LVM)||1000|
|Storage live migration|
|(non-CDROM) VDIs per VM||6|
|Snapshots per VM||1|
|Concurrent operations per pool||25|
- When HA is enabled, Citrix recommends increasing the default timeout to at least 120 seconds when more than 30 multipathed LUNs are present on a host. For information about increasing the HA timeout, see CTX139166 - How to Change High Availability Timeout Settings.