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  1. Hybrid Cloud Infrastructure Documentation
  2. HCIDOCS-675

Revise and align minimum CPU requirements for ODF deployments in Assisted Installer

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      Being reassessed and tested by the dev team

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    • HCIDOCS 2025#4, HCIDOCS 2025#5, HCIDOCS 2025#6, HCIDOCS 2025#7, HCIDOCS 2025#8
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      Description of problem:

      It is not clear what are the minimum CPU requirements for an OpenShift cluster with  ODF. The requirements in the documentation for ODF do not mention the number of CPU cores per installed data disks. 

      https://docs.redhat.com/en/documentation/red_hat_openshift_data_foundation/4.17/html/planning_your_deployment/infrastructure-requirements_rhodf#resource-requirements_rhodf
      But in the assisted installer, the minimum number of CPU cores required per host is defined as: 
      ODFPerHostCPUStandardMode + (diskCount * ODFPerDiskCPUCount) * assisted-service/internal/operators/odf/config.go https://github.com/openshift/assisted-service/blob/9feda639176e762ecdca0bdc350587fb8971fa8a/internal/operators/odf/config.go#L3-L13

      ```go
      type Config struct {
      ODFNumMinimumDisks int64 `envconfig:"ODF_NUM_MINIMUM_DISK" default:"3"`
      ODFPerDiskCPUCount int64 `envconfig:"ODF_PER_DISK_CPU_COUNT" default:"2"` // each disk requires 2 cpus
      ODFPerDiskRAMGiB int64 `envconfig:"ODF_PER_DISK_RAM_GIB" default:"5"` // each disk requires 5GiB ram
      ODFNumMinimumHosts int64 `envconfig:"ODF_NUM_MINIMUM_HOST" default:"3"`
      ODFPerHostCPUCompactMode int64 `envconfig:"ODF_PER_HOST_CPU_COMPACT_MODE" default:"6"`
      ODFPerHostMemoryGiBCompactMode int64 `envconfig:"ODF_PER_HOST_MEMORY_GIB_COMPACT_MODE" default:"19"`
      ODFPerHostCPUStandardMode int64 `envconfig:"ODF_PER_HOST_CPU_STANDARD_MODE" default:"8"`
      ODFPerHostMemoryGiBStandardMode int64 `envconfig:"ODF_PER_HOST_MEMORY_GIB_STANDARD_MODE" default:"19"`
      ODFMinDiskSizeGB int64 `envconfig:"ODF_MIN_DISK_SIZE_GB" default:"25"`
      }
      ``` * assisted-service/internal/operators/odf/odf_operator.go
      https://github.com/openshift/assisted-service/blob/9feda639176e762ecdca0bdc350587fb8971fa8a/internal/operators/odf/odf_operator.go#L268-L273

      ```go
      // worker in standard mode
      // Each ODF disk odf requires 2 CPUs and 5 GiB RAM
      return &models.ClusterHostRequirementsDetails{
      CPUCores: o.config.ODFPerHostCPUStandardMode + (diskCount * o.config.ODFPerDiskCPUCount),
      RAMMib: conversions.GibToMib(o.config.ODFPerHostMemoryGiBStandardMode + (diskCount * o.config.ODFPerDiskRAMGiB)),
      }, nil

      }
      ```

      Version-Release number of selected component (if applicable):

      4.17

      How reproducible:

      Deploy a new OpenShift Cluster via assisted installer with ODF. It shows: Require at least 12 CPU cores for worker role, found 2.

      Steps to Reproduce:

          1. Deploy a new cluster via assisted installer with 3 control-plane nodes and 3 compute-nodes
          2. Check the ODF for the installation
          3. At least 12 CPU cores is printed as minimal requirement.
          

      Actual results:

      12 cores per worker role is not the number presented in the ODF documentation as the minimum requirement. It is not clear if it involves 2 CPU cores for the worker node as minimum requirement from OpenShift also. 
      It count 8 CPU cores from the ODF minimum requirement per node and (2 * diskCount) CPU cores and that is not documented anywhere the number of CPU cores per data disk.

      Expected results:

      It is expected to be in sync the minimum requirement documented in ODF and assisted installer.

              rhn-support-tshwartz Talia Shwartzberg
              rhn-support-rludva Radomir Ludva
              Alona Paz, Dan Manor, Eran Ifrach
              Elia Jahshan Elia Jahshan
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                Created:
                Updated: