Extending datacenters to the public cloud:

 A specific pattern used toward hybrid computing involves extending datacenters to the public cloud. Many companies have significant investments in their immovable datacenters and while they can create a private cloud such as a VMWare cloud within the public cloud, they might find it costly to maintain both an on-premise cloud and one on the public cloud. A reasonable approach between these choices is to extend the existing datacenters to the public cloud. This article explores this pattern.

 

Although technology products are not referred to by their brands or product names in a technical discussion of an architectural pattern, it simplifies this narrative by providing a specific example of the technology discussed. Since many technological innovations are patented, it’s hard to refer to them without using product names. In this case, we use the example of a private cloud with VMWare cloud and refer to its products for manageability. A VMWare vCenter is a centralized management utility that can manage virtual machines, hosts, and dependent components. VMWare vSphere is VMWare’s virtualization platform, which transforms datacenters into aggregated computing infrastructures that include CPU, storage, and networking resources.

The pattern to extend the datacenter to VMWare Cloud on AWS uses Hybrid Linked Mode. Inventories in both places can be managed through a single VMWare vSphere Client interface. This ensures consistent operations and simplified administration and uses a VMWare Cloud Gateway Appliance. It can be used to manage both applications and virtual machines that are on-premises.

There are two mutually exclusive options for configuration. The first option installs the Cloud Gateway Appliance and uses it to link from the on-premises vCenter server to the cloud SDDC. The second option configures Hybrid Linked Mode from the cloud SDDC. The Hybrid Linked Mode can only connect one on-premises vCenter Server Enhanced Linked Mode domain and supports on-premises vCenter Server running more recent versions. When a cloud gateway appliance is connected to the Hybrid Linked Mode, there can be multiple vCenter Server connected to the appliance but when the cloud SDDC is directly connected to the Hybrid Linked Mode, there can be only one vCenter Server.

Different workloads can be migrated using either a cold migration or a live migration with VMWare vSphere vMotion. Factors that must be considered when choosing the migration method include virtual switch type and version, the connection type to the cloud SDDC, and the virtual hardware version.

A cold migration is appropriate for virtual machines that experience downtime. These virtual machines can be shut down, migrated and then powered back on.  The migration time is faster because there is no need to copy active memory. This holds true for applications as well.  A live migration, on the other hand, uses vMotion to perform rolling migration without downtime and is advisable for mission critical applications. The idea behind vMotion is that a destination instance is prepared and made ready and the switching from source to destination happens near instantaneously.

This pattern establishes promotes the visibility of existing infrastructure to the cloud.