Chapter 6. Subscriptions
6.1. Subscription offerings
Red Hat OpenShift Data Foundation subscription is based on “core-pairs,” similar to Red Hat OpenShift Container Platform. The Red Hat OpenShift Data Foundation 2-core subscription is based on the number of logical cores on the CPUs in the system where OpenShift Container Platform runs.
As with OpenShift Container Platform:
- OpenShift Data Foundation subscriptions are stackable to cover larger hosts.
- Cores can be distributed across as many virtual machines (VMs) as needed. For example, ten 2-core subscriptions will provide 20 cores and in case of IBM Power a 2-core subscription at SMT level of 8 will provide 2 cores or 16 vCPUs that can be used across any number of VMs.
- OpenShift Data Foundation subscriptions are available with Premium or Standard support.
6.2. Disaster recovery subscription requirement
Disaster Recovery features supported by Red Hat OpenShift Data Foundation require all of the following prerequisites to successfully implement a disaster recovery solution:
- A valid Red Hat OpenShift Data Foundation Advanced entitlement
- A valid Red Hat Advanced Cluster Management for Kubernetes subscription
Any Red Hat OpenShift Data Foundation Cluster containing PVs participating in active replication either as a source or destination requires OpenShift Data Foundation Advanced entitlement. This subscription should be active on both source and destination clusters.
To know how subscriptions for OpenShift Data Foundation work, see knowledgebase article on OpenShift Data Foundation subscriptions.
6.3. Cores versus vCPUs and hyperthreading
Making a determination about whether or not a particular system consumes one or more cores is currently dependent on whether or not that system has hyperthreading available. Hyperthreading is only a feature of Intel CPUs. Visit the Red Hat Customer Portal to determine whether a particular system supports hyperthreading.
For systems where hyperthreading is enabled and where one hyperthread equates to one visible system core, the calculation of cores is a ratio of 2 cores to 4 vCPUs. Therefore, a 2-core subscription covers 4 vCPUs in a hyperthreaded system. A large virtual machine (VM) might have 8 vCPUs, equating to 4 subscription cores. As subscriptions come in 2-core units, you will need two 2-core subscriptions to cover these 4 cores or 8 vCPUs.
Where hyperthreading is not enabled, and where each visible system core correlates directly to an underlying physical core, the calculation of cores is a ratio of 2 cores to 2 vCPUs.
6.3.1. Cores versus vCPUs and simultaneous multithreading (SMT) for IBM Power
Making a determination about whether or not a particular system consumes one or more cores is currently dependent on the level of simultaneous multithreading configured (SMT). IBM Power provides simultaneous multithreading levels of 1, 2, 4 or 8 for each core which correspond to the number of vCPUs as in the table below.
| SMT level | SMT=1 | SMT=2 | SMT=4 | SMT=8 |
|---|---|---|---|---|
| 1 Core | # vCPUs=1 | # vCPUs=2 | # vCPUs=4 | # vCPUs=8 |
| 2 Cores | # vCPUs=2 | # vCPUs=4 | # vCPUs=8 | # vCPUs=16 |
| 4 Cores | # vCPUs=4 | # vCPUs=8 | # vCPUs=16 | # vCPUs=32 |
For systems where SMT is configured the calculation for the number of cores required for subscription purposes depends on the SMT level. Therefore, a 2-core subscription corresponds to 2 vCPUs on SMT level of 1, and to 4 vCPUs on SMT level of 2, and to 8 vCPUs on SMT level of 4 and to 16 vCPUs on SMT level of 8 as seen in the table above. A large virtual machine (VM) might have 16 vCPUs, which at a SMT level 8 will require a 2 core subscription based on dividing the # of vCPUs by the SMT level (16 vCPUs / 8 for SMT-8 = 2). As subscriptions come in 2-core units, you will need one 2-core subscription to cover these 2 cores or 16 vCPUs.
6.4. Splitting cores
Systems that require an odd number of cores need to consume a full 2-core subscription. For example, a system that is calculated to require only 1 core will end up consuming a full 2-core subscription once it is registered and subscribed.
When a single virtual machine (VM) with 2 vCPUs uses hyperthreading resulting in 1 calculated vCPU, a full 2-core subscription is required; a single 2-core subscription may not be split across two VMs with 2 vCPUs using hyperthreading. See section Cores versus vCPUs and hyperthreading for more information.
It is recommended that virtual instances be sized so that they require an even number of cores.
6.5. Subscription requirements
Red Hat OpenShift Data Foundation components can run on either OpenShift Container Platform worker or infrastructure nodes, for which you can use either Red Hat CoreOS (RHCOS) or Red Hat Enterprise Linux (RHEL) 8.4 as the host operating system. RHEL 7 is now deprecated. OpenShift Data Foundation subscriptions are required for every OpenShift Container Platform subscribed core with a ratio of 1:1.
When using infrastructure nodes, the rule to subscribe all OpenShift worker node cores for OpenShift Data Foundation applies even though they don’t need any OpenShift Container Platform or any OpenShift Data Foundation subscriptions. You can use labels to state whether a node is a worker or an infrastructure node.
For more information, see How to use dedicated worker nodes for Red Hat OpenShift Data Foundation in the Managing and Allocating Storage Resources guide.
