VIA images the rack components in a pre-determined order, which is determined by the availability of network route to the different components of the rack. All switches are imaged first. This enables VIA to access the servers through the switches for imaging. The imaging order is as follows.

  1. Management switch

    The management switch is the main access gateway through which the Cloud Foundation management data is routed. The management ports of the ToR and inter-rack switches are connected to the management switch. The data ports of the ToR switches are also connected to the management switch. VIA is connected to the rack through a designated port on the management switch. It is therefore required that the management switch is the first component imaged by VIA in order to obtain access to the other components of the rack.

  2. ToR switches and Inter-rack switches (inter-rack switches are on rack 2 only)

    ToR and inter-rack switches are imaged in parallel.

    ToR switches provide connectivity to servers in each rack out to inter-rack switches. The first pair of ToR switches provide connectivity to your datacenter network. Inter-rack switches inter-connect multiple racks enabling a scale out architecture for the datacenter. They create an stretched L2 backplane between racks.

  3. Servers

    Servers must be rebooted after the switches are imaged. They are then imaged in parallel.

For each component that is being imaged, the following tasks are performed.

  1. Discovery

    Rack components are discovered using the DHCP service running on the VIA VM. The DHCP Service uses the device type information to identify the device being discovered. Apart from the device type information, the DHCP service also uses hardware vendor specific strings to determine whether the switch being imaged is a management, ToR, or inter-rack switch.

    The first component to be discovered is the management switch. The DHCP service hands out a pre-determined IP address for the management switch followed by a PXE image specific to the management switch.

    After the management switch is imaged, the ToR and inter-rack switches are discovered and imaged. The ToR switch enables discovery of the data network of the servers which is used to receive the installation image delivered by the DHCP service.

  2. Image installation

    Image installation refers to installing software on the components to make them operational. The software depends on the component type - an Operating System for switches and a Hypervisor for servers.

  3. Configuration

    This step in the imaging process ensures that the components of the rack work like a homogenous system. Configuration of each rack component is different. If any configuration step fails for the management, ToR, or inter-rack switches, the imaging run stops at that point. You must resolve the issue before you can proceed with imaging. If a configuration step fails for a server, you can skip that server and continue imaging the remaining servers.