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Chapter 2. Recommended specifications
2.1. Undercloud
For best performance, install the undercloud node on a physical server. However, if you use a virtualized undercloud node, ensure that the virtual machine has enough resources similar to a physical machine described in the following table.
Table 2.1. Recommended specifications for undercloud node
| Counts | 1 |
| CPUs | 12 cores, 24 threads |
| Disk | 500GB root disk (1x SSD or 2x hard drives with 7200RPM; RAID 1) 500GB disk for swift (1x SSD or 2x hard drives with 7200RPM; RAID 1) |
| Memory | 64 GB |
| Network | 10 Gbps network interfaces |
2.2. Overcloud Controller nodes
When planning for Controller nodes, storage planning is important. OpenStack Telemetry Metrics (gnocchi) and OpenStack Image Storage (glance) services are I/O intensive. For best performance, Red Hat recommends using Ceph Storage for Telemetry and Image Storage because the overcloud moves the I/O load to the Ceph OSD servers. If your deployment does not include Ceph storage, Red Hat recommends a dedicated disk or node for OpenStack Object Storage (swift) that OpenStack Telemetry Metrics (gnocchi) and OpenStack Image Storage (glance) services can use. If using OpenStack Object Storage (swift) on Controller nodes, use an NVMe device separate from the root disk to reduce disk utilization when storing object data.
Table 2.2. Recommended specifications for Controller nodes when you use Ceph Storage nodes
| Counts | A least 3 Controller nodes with all controller services contained within a single Controller role. Optionally use composable services and custom roles if required. |
| CPUs | 2 sockets each with 12 cores, 24 threads |
| Disk | 500GB root disk (1x SSD or 2x hard drives with 7200RPM; RAID 1) |
| Memory | 128 GB |
| Network | 25 Gbps network interfaces or 10 Gbps network interfaces. If using 10 Gbps network interfaces, use network bonding to create two bonds:
|
Table 2.3. Recommended specifications for Controller nodes when you do not use Ceph Storage nodes
| Counts | A least 3 Controller nodes with all controller services contained within a single Controller role. Optionally use composable services and custom roles if required. |
| CPUs | 2 sockets each with 12 cores, 24 threads |
| Disk | 500GB root disk (1x SSD or 2x hard drives with 7200RPM; RAID 1) 500GB disk for Swift (1x SSD or 2x hard drives with 7200RPM; RAID 1) |
| Memory | 128 GB |
| Network | 25 Gbps network interfaces or 10 Gbps network interfaces. If using 10 Gbps network interfaces, use network bonding to create two bonds:
|
2.3. Overcloud Compute nodes
Table 2.4. Recommended Compute node specifications
| Counts | Red Hat has tested a scale of 300 nodes. |
| CPUs | 2 sockets each with 12 cores, 24 threads |
| Disk | 500GB root disk (1x SSD or 2x hard drives with 7200RPM; RAID 1) 500GB disk for glance image cache (1x SSD or 2x hard drives with 7200RPM; RAID 1) |
| Memory | 128 GB (64 GB per NUMA node); 2GB is reserved for the host out of the box. With Distributed Virtual Routing, increase the reserved RAM to 5 GB. |
| Network | 25 Gbps network interfaces or 10 Gbps network interfaces. If using 10 Gbps network interfaces, use network bonding to create two bonds:
|
2.4. Red Hat Ceph Storage nodes
Table 2.5. Recommended Ceph Storage node specifications
| Counts | A minimum of 5 nodes with three-way replication is required. With all-flash configuration, a minimum of 3 nodes with two-way replication is required. |
| CPUs | 1 Intel Broadwell CPU core per OSD to support storage I/O requirements. If you are using a light I/O workload, you might not need Ceph to run at the speed of your block devices. For example, for some NFV applications, Ceph supplies data durability, high availability, and low latency but throughput is not really a target, so it is acceptable to supply a little less CPU power. |
| Memory | Allow 5 GB RAM per OSD. This is required for caching OSD data and metadata to optimize performance, not just for the OSD process memory. For hyper-converged infrastructure (HCI) environments, calculate the required memory in conjunction with the Compute node specifications. |
| Network | Ensure the network capacity in MB/s is higher than the total MB/s capacity of the Ceph devices to support workloads that use a large I/O transfer size. Use a cluster network to lower write latency by shifting inter-OSD traffic onto a separate set of physical network ports. To do this in Red Hat OpenStack Platform, configure separate VLANs for networks and assigning the VLANs to separate physical network interfaces. |
| Disk | Solid-State Drive (SSD) Journaling reduces I/O contention on hard disk drives (HDD), which increases the speed of write IOPS, but SSDs have zero effect on read input/output operations per second. If using SATA/SAS SSD journals, you typically need a ratio of SSD:HDD of 1:5. If using NVM SSD journals, you can typically use a SSD:HDD ratio of 1:10 or even 1:15 in cases where the workload is read-mostly. However, if this ratio is too high, the SSD journal device failure can affect the OSDs. |
For more information, see Red Hat Ceph Storage for the Overcloud.
For more information on changing the storage replication number, see Pool, PG, and CRUSH Configuration Reference in the Red Hat Ceph Storage Configuration Guide.
