Virtualization was dominated by on-premises enterprise virtualization, and on-premises private clouds were the primary sourcing model for VMs offered as a service – for a few years. Certainly not true today.
In 2011, roughly 3 percent of all virtual machines (VMs) were sourced in public cloud IaaS providers (mainly Amazon). That was also roughly equal to the number of VMs being delivered in true on-premises private clouds (standard offerings through self-service with automated delivery – NOT custom-provisioned, NOT manually delivered).
A lot’s changed in three years.
The overall number of active VMs has tripled. The number of VMs in true on-premises private clouds has also tripled. But the number of active VMs in the public cloud has increased by a factor of twenty. Public cloud IaaS now accounts for about 20 percent of all VMs – and there are now roughly six times more active VMs in the public cloud than in on-premises private clouds.
At the same time, isolation options from public cloud providers are growing – more and more are offering semi-private, virtual-private, or fully-private capabilities.
There’s a fair amount of waste here – life cycle management and governance for VMs in the public cloud are not nearly as rigorous as management and governance in on-premises private clouds. Perhaps 30-50 percent of the VMs in the public cloud are zombies (private clouds have zombies and life cycle management challenges, too – just not as bad).
Also, the demographic of workloads in each are very different – public cloud VMs are much more likely to be used for horizontally-scalable, cloud-friendly, short-term instances, while private cloud tends to have much more vertically-scalable, traditional, long-term instances. There are certainly examples of new cloud-friendly instances in private clouds, and examples of traditional workloads migrated to public cloud IaaS, but those aren’t the norm. New stuff tends to go to the public cloud, while doing old stuff in new ways tends to go to private clouds.
And new stuff is simply growing faster.