Prior to the release of vCloud Director v9.0, Cloud Service Providers built infrastructure resilience and increased availability by distributing elements of the resource platform, managed by vCloud Director, across multiple sites. While providing availability benefits to customers, doing so brought operational challenges. So, does the introduction of multisite capabilities within the latest release make these older topology models unnecessary? The answer, as with many elements of infrastructure design, is “it depends”.

While the benefits that can be realized remain, it is possible to simplify the management of a vCloud Director deployment using the multisite enhancements in v9.0. Looking at the two stretched vCloud Director models from Section 2.3, the “dual vCenter Server” model offers the ability to manage two separate resource environments from a single UI, whereas the “single vCenter Model” model offers the ability to manage two separate resource environments as if they were a single environment. Both models also brought with them additional complexity in recovering the management platform in the event of a failure at the site at which vCloud Director was operating.

The dual vCenter Server model’s key benefit was the single UI across two sites, a feature that is replicated more elegantly in the multisite capability of v9.0. The dual vCenter Server model requires infrastructure for the “standby” site to recover the management platform in the event of a failure at the “active” site. If that is replaced by an active vCloud Director at both sites with association enabling access to resources at both sites, no additional infrastructure is required, and the complexity of recovering vCloud Director and the rest of the management infrastructure to a remote site is replaced with a simpler operation at both sites.

The “stretched vCenter Server” model’s key benefit is a more seamless distribution, operation, and migration of resources across two discrete locations. This use case is not addressed in the current version of vCloud Director because the multisite resilience was previously delivered through the vSphere resource layer rather than the UI. If a Cloud Service Provider wants to continue to offer this level of resilience, at least in the current version of vCloud Director, the stretched vCenter Server model still has a place.

What if the Service Provider already has one, or both, of these multisite models in place within their product offerings? Does the upgrade of a production environment force the provider to adopt multisite association immediately? The simple answer is no. While it can be argued that the introduction of multisite association in place of the dual vCenter Server model offers some operational simplification, the introduction of a second vCloud Director at the “standby” site, and migration of that site’s vCenter Server and associated resources, might be outside of the immediate resource budget. The simplest option might be to leave any existing stretched vCloud Director environments as they are initially, and then review the benefits, to both customers and the provider, of moving to a multisite associated model as a separate project. The following figure illustrates how existing stretched vCloud Director instances can be included in a multisite association.

 

 

This figure shows the inclusion of existing stretched single and dual vCenter Server vCloud Director multisite instances into a site association mesh which also includes a single-site, non-stretched instance. The sites represent the availability zones within a single region. The Oregon zone is comprised of two data centers under a single, stretched vCloud Director each data center with their own vCenter Server. The Nevada zone has two data centers under a stretched vCloud Director and stretched vCenter Server. For simplicity, the California zone is shown with as a single data center. This could represent a provider deployment following the upgrade to v9.0 in an existing three vCloud Director region. The Oregon zone could then, as a follow-up project, be split into two discrete vCloud Director instances, each joined to the regional mesh as shown in the following figure.

 

Although not all associations are shown, the provider makes sure that the required site associations are in place to enable tenants to establish organization associations as appropriate.