In general, VMware recommends that the number of vCloud Director cell instances = n + 1, where n is the number of vCenter Server instances providing compute resources for cloud consumption. Based on the Service Definition, two vCloud Director cell instances should be sufficient and allow for upgradability (upgrading one vCloud Director cell, then the other) and high availability.
It is important for vCloud Director to be able to spread and run services in case of hardware failures and load balance them on available cells as best as it can. This article describes how the Kemp Loadmaster is able to balance client connections to the vCloud Director portal and ensures a highly available multi cell deployment by monitoring services an response times.
The Console Proxy and web portal are running on every cell and are stateless. All instances are capable of doing work so failure of any one component does not affect user requests as they are redirected by the load balancer. In a one-armed configuration, the Virtual Servers and the VDC cells are configured on the same subnet. The LoadMaster connects to the Layer 2 network through a single interface, eth0. This architecture covers load balancing of multiple vCloud Director sells within the same site.
The Loadmaster service should be configured to check the health and response time of the individual vCloud Director cells. Since each cell responds via HTTPS, this can be configured quickly via the IP and API end point URL. Generally services are checked every few-30 seconds based on load. A good starting point is 5 seconds. Example GUI URL - https://my.cloud.com/cloud/
Viktor van den Berg over at viktorious.nl has written an extensive article about load balancing vCloud Director cells with pfSense - vCloud Director Howto: Load balancing with free pfSense
Viktor van den Berg over at viktorious.nl has written an extensive article about load balancing vCloud Director cells with pfSense - vCloud Director Howto: Load balancing with free pfSense
