How to Add or Remove OpenStack Hardware Nodes

Introduction

OpenMetal Private Clouds can have hardware nodes added to them, increasing the available compute and storage resources to your cloud. Similarly, hardware nodes can be removed should resources no longer be required. In this guide we explain best practices when selecting new hardware nodes for your cloud. Next we cover how to add nodes, which types of nodes you can add, and the process for removing nodes from your cloud.

Cloud Hardware Selection

In this section we outline the types of clouds offered, the types of nodes you can add to your cloud, and best practices when choosing hardware for your Private Cloud. Additionally we explain conditions under which your cloud's Ceph cluster is affected when adding hardware.

Types of Private Clouds

Private Clouds come in three sizes: Medium, Large, and XL. Each is a cluster of three servers.

Sizes are versioned. As new hardware becomes available we add a version, so a size exists in more than one generation and older generations stay available for a time.

Figure 1: Hardware Catalog

The hardware catalog lists each size with its CPU, cores, storage, RAM, and price, for the location and term you choose. GPU sizes are listed alongside them.

To work out which size fits your workload, book a meeting with our team.

Types of Nodes

A node is added in one of two roles:

• Storage + Compute: a full-capability node providing both storage and compute. It handles data persistence as well as workload processing.
• Compute Only: a dedicated processing node for scaling compute capacity. Its storage is available for ephemeral use.

Nodes come in the same sizes as clouds, with XXL and GPU nodes available in addition. Some sizes have variants, such as a high frequency CPU option or a storage configuration with more drive bays. Previous generations stay available alongside the latest hardware, so node sizes carry a version in the same way cloud sizes do.

The Benefit of Homogeneous Clouds

By default, Private Clouds are hyper-converged and include a Ceph deployment. Generally speaking, Ceph is only as fast as your slowest node allows, though there are caveats to this. Ceph could be impacted by the type of nodes added to a cluster due to potential differences in hardware, such as performance disparity between storage provided by HDDs, SSDs or NVMes. Having a homogeneous cluster of similarly equipped nodes will have the best results in terms of performance and data density. Additionally, while you can add any hardware node to your cloud, the Network Interface Cards (NICs) for each designation of node may have a different maximum throughput. If a node with a 1Gbit NIC is added to a cluster with nodes having 10Gbit NICs, the internal network traffic is limited by the additional node.

Adding Hardware Nodes to a Cloud

In this section, we explain the steps needed to add hardware nodes to your cloud.

The following demonstrates adding a node to an existing cloud.

How to add a Hardware Node

Navigate in OpenMetal Central to Cloud Assets Page

First navigate in OpenMetal Central to your cloud's details page. Next follow the Assets link on the left. This page shows you details about your cloud's current assets and also allows you to add a new hardware node. To add a new hardware node, select the Add Hardware button located at the top right.

Figure 2: Add Hardware

View Hardware Node Types

The next screen lists the hardware you can add.

Figure 3: Available Hardware List

Each row gives the CPU, cores and threads, included storage, drive bays, installed and maximum RAM, egress, monthly price, and delivery time. The latest hardware is listed first, with previous generations below it.

Choose a size and select Add to Cart.

Configure the Node

Set the deployment target to your existing cloud, then choose the node role, the number of servers, the memory, and the location. Drives use the default configuration unless you customize them.

Figure 4: Configure the Node

Select Save, then place the order. A confirmation is returned once the order is processed.

Figure 5: Hardware Addition Success

Note -- Adding a hardware node can take around an hour to complete. An email is sent to the primary account's address when complete.

Verify Hardware Addition Success

Navigate to your cloud's assets page to confirm the newly added node.

Figure 6: Successful Hardware Node Addition

Removing Hardware Nodes from a Cloud

In this section, we outline the steps required to remove a hardware node from your cloud.

Copy any data you need from the node before removing it. Removal cannot be undone.

Consider Before Removing

At all times, your cloud must have three hyperconverged control plane nodes running to have a fully functioning OpenStack cloud. As such, the node being removed cannot be a control plane node.

Control plane nodes in OpenMetal Central are prefixed with Cloud Core and can be distinguished from other nodes by inspecting the Class column in your cloud's assets page in OpenMetal Central.

For example, in the following screenshot the three nodes whose class begins with Cloud Core are control plane nodes:

Figure 7: Control Plane nodes

The remaining node, classified Storage and Compute - Large v5, is not a control plane node, meaning it does not run all the core OpenStack services.

Initial Preparation

To prepare for removal of a hardware node, migrate any instances to another node that has compute services running. All hyperconverged nodes run OpenStack's compute service. For instruction regarding migrating instances to another node, see the How to Live Migrate Instances guide.

How to Remove a Hardware Node from a Cloud

Open the three dots menu at the end of the node's row and choose Remove.

Figure 8: Node actions menu

The same menu holds the other per-node actions: Details, Edit Node, IPMI Access, and the power and restart controls.