A flexVDI platform can easily scale up by adding new Hosts. The flexVDI Manager will balance the resources allocated to Pools among all the available Hosts, and run Guests in any of them as needed. flexVDI uses the OCFS2 clustered filesystem to grant exclusive access to Guests's images by any Host, and to provide cluster consistency in case of communication failures. This chapter explains how to configure and use a cluster of flexVDI Hosts.

Adding a new Host to the cluster

Adding a new Host to a flexVDI cluster is as easy as following these two simple steps:

1. Install the flexVDI distribution in the new Host. Follow the Getting Started guide until you perform the Basic host configuration (do not install a new Manager, there is only one Manager instance per cluster). Be careful to create the same virtual bridges as in the other Hosts, so that they map to the same subnets.
2. Register the Host with your flexVDI Manager instance. Remember that this is done with flexVDI Config. In the main menu, go to "Manager" and select "Register". This time, flexVDI Config will ask you the Manager IP address first, and then the Manager password. After the Host is registered, the SSH keys will be updated in all the Hosts.

Once this is done, you will see the new Host appear in flexVDI Dashboard, and you can start using it right away.

Replacing a failed Host

If you are adding a Host that substitutes another failed one, the best way is to use the same domain name and IP address. In this way, the Manager will replace the previous Host. You can also remove the old Host with the Dashboard and then add the new one.

Removing a Host from the cluster

Removing a host from the flexVDI cluster can be done with the Dashboard. The only requirement is that no Guest is running in the Host, and that it is disabled. Then, just right-click on the desired Host and select the "Remove" option.

Accessing shared storage

flexVDI 3.1 supports three types of storage: OCFS2, Gluster and External. All three of them make it possible to access a shared storage space among the hosts of your cluster. Usually, you will first need to make one or more disk devices available to the host. These disks can be, for instance, physical SAS disks or iSCSI targets. SAS disks are autodetected during boot. iSCSI targets must be first configured with the iscsiadm tool. In order to discover and configure the different types of shared storage that can be made available in a flexVDI cluster, read the Red Hat storage management documentation.

Next, flexVDI Agent must be aware of these disks. By default, it only discovers new disk devices on startup. If you configure new devices without rebooting your host, you will have to restart the service:

# systemctl restart flexvdi-agent

Otherwise, you can also configure flexVDI Agent to scan the system for new disks periodically. This is not recommended unless you have a good reason, as it is an expensive operation. Edit /etc/flexvdi/flexvdi-agent.conf like this to set a period of 30 seconds:

[monitors]
...
disks = 30

Once your hosts have access to shared storage, read the section on setting up flexVDI storage with flexVDI Dashboard. The following sections explain additional details on how to set up the different storage technologies supported by flexVDI, and how to move your flexVDI Manager instance to a shared storage Volume to provide high availability.