Converged and hyper-converged infrastructures have similar names, but they take very different approaches and solve different types of problems.
Converged infrastructure (CI) helps remove risk from a large virtualization deployment. Hyper-converged infrastructure (HCI) represents a rethinking of VM delivery, and it aims to simplify operation of a virtualization platform. Either converged or hyper-converged infrastructure appliances can deliver a faster time to value than assembling a virtualization platform from disparate components, but their resulting platforms will have different characteristics.
Converged infrastructure appliances
A converged infrastructure appliance is pre-configured to run a certain number of VMs, and it's ready to be connected to an existing data center network and power supply from the time it's built. Vendors build these appliances with components that include a storage array, some servers, network switches and all the required cables and connectors. Vendors assemble and test all of these components before delivering them to customers, and they control every aspect of the build, down to the certified firmware and driver levels for each part.
A small converged infrastructure appliance can take up just half a data center rack, and the largest might be five full racks. Usually, deployment involves professional services from the vendor, and every update requires more professional services. The aim of CI is to take the risk out of deploying a virtualization platform by having the vendor design and support the same platform across multiple customers. It is usually not designed to scale in place; for more capacity, organizations must buy additional complete converged infrastructure appliances.
Hyper-converged infrastructure appliances are built around a single x86 server, and a group of appliances are configured together as a cluster that organizations can expand and contract by adding or removing appliances.
HCI puts an emphasis on simplified VM management. It usually also includes some sort of backup capability and often a disaster recovery (DR) function. (Many hyper-converged products integrate with the public cloud for backup and DR.)
A significant feature of hyper-converged infrastructure appliances is that in-house IT professionals, rather than vendors' professional services staff, can complete most functions, from initial deployment to adding nodes to the entire update process.
Converged or hyper-converged?
The first consideration when choosing converged or hyper-converged infrastructure is scale. A half rack of CI appliances will run 100 or more VMs, whereas five racks will run thousands of VMs. CI is not for small offices or small businesses. It's suited for enterprises.
The second aspect is that CI is about reducing risk, even if that increases cost. All of the professional services that surround CI are areas where the vendor is paid to reduce the customer's risk. Organizations buy CI for guaranteed outcomes, so they tend to be in risk-averse industries, such as banking, insurance, government and healthcare.
Hyper-converged infrastructure appliances are popular with organizations that do not want to think about the hardware or software underneath their VMs. These organizations want to manage a fleet of VMs with minimal effort because the value is in the applications inside those VMs, rather than the servers or hypervisors on which they run. HCI is ideally suited for scale-out workloads, such as VDI, or for nonproduction uses, such as test and development.
Some hyper-converged infrastructure appliances operate with just one or two nodes at a site. This makes them suitable for remote or branch office deployments, particularly where there are a large number of branches, such as in a retail chain. HCI's built-in data protection is popular in these scenarios because it reduces the risk of data loss at the branch and, in some cases, allows one branch to provide DR capacity for another.