Deployment Limits for Red Hat OpenStack Platform

Updated -

These limits for Red Hat OpenStack Platform components can be used to help design and scale OpenStack deployments. For more information on configuration options, see Recommended Practices for OpenStack, and the OpenStack documentation.

Table of Contents

  1. Networking service (Neutron)
  2. Compute service (Nova)
  3. Image service (Glance)
  4. Orchestration service / Template (Heat)
  5. Block Storage service (Cinder)
  6. Identity service (Keystone)

Networking service (Neutron)

Area Maximum Limit Notes
Number of logical networks in the environment using VLAN 4,094 This is the number of unique networks when using VLANs (12-bit VID in 802.1q).
Number of logical networks in the environment using NVGRE / VXLAN 16,000,000 This is the number of unique networks when using NVGRE (24-bit TNI) or VXLAN (24-bit VNI).
Number of logical networks per compute node 4,094 This assumes that you are using the ML2/Open vSwitch plugin. OVS 'br-int' uses local VLANs to separate traffic on the node.
Number of logical networks served by a network node 4,094 This assumes that you are using the ML2/Open vSwitch plugin. OVS 'br-int' uses local VLANs to separate traffic on the node.
Number of external networks Topology-dependent The maximum limit is the sum of the logical networks served by a network node or compute node, if OpenStack is set as a provider network on the compute node.
Number of routed networks Unlimited
Number of gateways Unlimited Some versions of Open vSwitch limit the number of namespaces to 1,000. This can impact the number of gateways.
Number of network pools Unlimited
Number of load balancers Unlimited This is limited by the number of processes you can start on the machine. Some versions of Open vSwitch limit the number of namespaces to 1,000. This can impact the number of load balancers.

Compute service (Nova)

Area Maximum Limit Notes
Number of virtual machines per KVM host 16384 This is limited by the operating system limits for process counts and open files.
Allocated RAM per KVM host 64TB For more information, see Red Hat Enterprise Linux technology capabilities and limits.
Number of virtual CPUs per virtual machine 160, 240 or 288 The limit was raised to 288 in RHEL 7.3. For RHEL 7.1 and RHEL 7.2, the limit is 240. In previous versions of RHEL, the limit is 160.
RAM per virtual machine 4000GB For more information, see Virtualization limits for Red Hat Enterprise Linux with KVM.
Virtual machine swap file size System limits The limit is the available disk space.
Virtual NICs per virtual machine 28 This is determined by the number of PCI slots and the number of available slots. If there are 32 slots, then slots are allocated for video, PIIX, balloon, and disk, which leaves 28 slots for NICs. If other slots are active, then the maximum may be lower.
Video memory per virtual machine Driver-dependent Different drivers have different performance limits.
Concurrent remote console connections to a virtual machine 65000 Limited by the number of TCP ports available that can opened against any single IP address. This will be something less than 65535 per compute host. Since a single console server targets many hosts, you'll in fact have a 65536 concurrent connection limit across everything served by that nova console host
Serial ports per virtual machine 2
Serial ports per virtual machine with virtio-console Many
Number of cells per region 1 Multi-cells Cells V2 is Technology Preview and not supported.
Number of instances No known tested limit There is no limit on the number of instances in a cloud, but the sizing of the environment, including controllers, can affect the practical limit.
Number of hosts No known tested limit There is no limit on the number of hosts in a cloud, but the sizing of the environment, including controllers, can affect the practical limit.

Image service (Glance)

Area Maximum Limit Notes
Number of images Unlimited The practical limit depends on the underlying database performance and back end storage type.

Orchestration service / Template (Heat)

Area Maximum Limit Notes
Number of templates Relative to projects The number of templates is related to the number of projects. With the default settings, there can be no more than 100 * the number of projects.
Number of virtual machines per template 1,000 This is a default configuration setting.
Number of templates per project 100 This is a default configuration setting.

Block Storage service (Cinder)

Area Maximum Limit Notes
Number of volumes Unlimited Specific databases may have relevant performance limits. No limits are imposed through the OpenStack configuration.
Number of concurrent active volumes Unlimited This is the control path component. The prospective volume is the raw database. The storage database may have limits on the number of active volumes.
Number of independent disks Unlimited
Number of unique storage classes Unlimited
Number of back end storage classes Unlimited
Number of mounted volumes per host Unlimited For iSCSI/FC: 10,000 devices on the system. 1024 multipathed devices. Depending on the storage backend, cinder driver, HBA driver, etc. additional limits may be in place.
Number of mounted volumes per virtual machine 26 Maximum is 26 volumes. Limit is defined by the compute component. Working to increase it

Identity service (Keystone)

Area Maximum Limit Notes
Number of regions Unlimited There is no technical limit within OpenStack, but overall performance depends primarily on the underlying database performance.
Total number of users Unlimited There is no technical limit within OpenStack, but overall performance depends primarily on the underlying database performance.
Number of projects Unlimited There is no technical limit within OpenStack, but overall performance depends primarily on the underlying database performance.
Number of users per project Unlimited There is no technical limit within OpenStack, but overall performance depends primarily on the underlying database performance.
Number of active concurrent users Unlimited There is no technical limit within OpenStack, but other practical performance limits apply.

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1 Comments

Minor typo? Copy/paste error?

Number of hosts Unlimited   There is no limit on the number of instances in a cloud, but the sizing of the environment, including controllers, can affect the practical limit.

Should probably be:

Number of hosts Unlimited   There is no limit on the number of ****HOSTS**** in a cloud, but the sizing of the environment, including controllers, can affect the practical limit.