This section discusses the hardware, software, and networking prerequisites for installing Rackspace Private Cloud Software. It also discusses concepts behind availability zones and high availability in Rackspace Private Cloud Software.

Hardware Requirements

OpenCenter and Chef Server Requirements

Cluster Node Requirements

Deploying OpenCenter in an All-VM Environment

Software Requirements

Network Requirements

Preparing For the Installation

Node Access Considerations

Instance Access Considerations

High Availability Concepts

Availability Zone Concepts

Hardware Requirements

Rackspace has tested two hardware-based scenarios for Rackspace Private Cloud Software deployment, with different hardware requirements.

• A physical device for each required node: an OpenCenter server, a Chef server, an OpenStack Nova Controller node, and additional physical machines with OpenStack Nova Compute nodes as required.
• One physical device with VMs configured for the OpenCenter Server and Chef server, and the OpenStack Nova Controller node installed on the host, and additional physical machines for the OpenStack Nova Compute nodes as required. For information about this configuration, refer to "Installing OpenCenter in a Virtual Machine Configuration".

OpenCenter and Chef Server Requirements

Rackspace recommends that the OpenCenter server meets the following minimum requirements:

• 8 GB RAM
• 144 GB disk space
• Dual socket CPU with dual core. A dual socket CPU with a hex core (for a total of 6-12 cores) will provide better performance.

The Chef server hardware should meet the following requirements:

• 16 GB RAM
• 144 GB disk space
• Dual socket CPU with dual core, or single socket quad core

Cluster Node Requirements

Each node in the cluster will have the OpenCenter agent installed on it. The hardware requirements vary depending on the purpose of the node. Each device should support VT-x. Refer to the following table for detailed requirements.

CPU overcommit is set at 16:1 VCPUs to cores, and memory overcommit is set to 1.5:1. Each physical core can support up to 16 virtual cores; for example, one dual-core processor can support up to 32 virtual cores. If you require more virtual cores, adjust your sizing appropriately.

Deploying OpenCenter in an All-VM Environment

For testing purposes, it is also possible to deploy Rackspace Private Cloud Software on a group of virtual machines, such as a group of Rackspace Cloud Servers. The virtual machines should meet specifications similar to the standard hardware specifications, though it is possible for the Chef server, Controller, and Compute nodes to be as small as 8 GB if you are only doing proof-of-concept tests.

Software Requirements

The device on which OpenCenter Server is installed and all OpenCenter-managed devices must be using one of the following operating systems:

• Ubuntu 12.04
• CentOS 6.3
• RHEL 6.3 or 6.4

The GUI package can also be installed on OS X.

Network Requirements

Internet access is required to complete the installation, so ensure that the devices that you use have internet access to download the installation files.

Rackspace Private Cloud Software creates a FlatDHCP network in multi_host mode, in which nova-network software is installed and configured on each server that is running nova-compute. Further conceptual information about Flat DHCP networking is available in the OpenStack Compute Administration Manual. Refer to the following topics:

• Configuring flat DHCP networking
• Libvirt Flat DHCP Networking

Preparing For the Installation

Before you begin, have the following networking information prepared and available:

• The Nova public network in CIDR format.
• The Nova public network interface (such as eth0).
• The Nova VM network bridge (such as br100).
• Optional NAT exclusion CIDR range or ranges for networks configured with a DMZ,
• The name of the Nova cluster.
• A password for an admin OpenStack user.
• Nova management network address in CIDR format.
• The interface of the VM network for the Compute notes (such as eth1).
• The name of the default availability zone.
• The VM network CIDR range.
• The Nova internal network CIDR range that you want to assign to each Controller and Compute node.

Node Access Considerations

All nodes within the OpenCenter environment must be able to access one another. Provided that the nodes on which the agent is installed have outbound connectivity to the OpenCenter server, the nodes can be physically located anywhere. All communication between the server and agent runs from the agent to the server.

Currently, if you delete the agent from a node, you will have to manually delete the node from the server with the opencentercli node delete command in the command line interface.

Instance Access Considerations

By default, the instances that you create in the OpenStack cluster can only be publicly accessed via NAT by assigning floating IP addresses to them. Before you assign a floating IP address to an instance, you must have a pool of addresses to choose from. Your network security team must provision an address range and assign it to your environment. These addresses need to be publicly accessible. Floating IP addresses are not specified during the installation process; once the Controller node is operational, you can add them with the nova-manage floating create --ip_range command. Refer to "Managing Floating IP Addresses".

You can also make the instances accessible to other hosts in the network by default by configuring the cloud with a network DMZ. The network DMZ range cannot be the same as the nova fixed network range. Specifying a DMZ enables NAT-free network traffic between the virtual machine instances and resources outside of the nova fixed network. For example, if the nova fixed network is 10.1.0.0/16 and you specify a DMZ of 172.16.0.1/12, any devices or hosts in that range will be able to communicate with the instances on the nova fixed network.

To use the DMZ, you must have at least two NICs on the deployment servers. One NIC must be dedicated to the VM instances.

High Availability Concepts

Rackspace Private Cloud Software has the ability to implement support for high availability for all Nova service components and APIs, Cinder, and Keystone, and Glance, as well as the scheduler, rabbitmq, and mysql. HA functionality is powered by Keepalived and HAProxy.

There are three methods through which Rackspace Private Cloud Software cookbooks implement high availability in your cluster:

• mysql master-master replication and active-passive failover: mysql is installed on both controller nodes, and master-master replication is configured between the nodes. Keepalived manages connections to the two nodes, so that only one node receives reads/writes at any one time. 
• rabbitmq active/passive failover: rabbitmq is installed on both controller nodes. Keepalived manages connections to the two nodes, so that only one node is active at any one time.
• API load balancing: All services that are stateless and can be load balanced (essentially all the APIs and a few others) are installed on both controller nodes. HAproxy is then installed on both nodes, and Keepalived manages connections to HAproxy, which makes HAproxy itself HA. Keystone endpoints and all API access goes through Keepalived.

Availability Zone Concepts

Availability zones enable you to manage and isolate different nodes within the environment. For example, you may want to isolate different sets of Compute nodes to provide different resources to customers. If one availability zone experiences downtime, other zones in the cluster will not be affected.

When you create a Nova cluster with OpenCenter, it is created with a default availability zone, and all Compute nodes will be assigned to that zone. You can create additional availabilty zones within the cluster as needed.