Zokahn -Personal Blog-

30Apr/14Off

Virtualization is not cloud!

There is a distinct difference between virtualization as used in organizations for over a decade and the new evolution in IT called 'cloud'. In classic virtualization the focus is on the virtual machine itself. The compute resources, the virtualization hosts, are made to host multiple instances of a guest OS, possible connected to predefined networks and storage volumes. Manual or automated effort is needed to connect the VM to needed resources, which have to exist or need to be created up front for the VM can utilize it's resources.

In virtualization the VM can be tailored to the users exact specifications, a VM can be made to scale-up (add more compute resources to the single VM) to match a single application needs. A VM is typically nurtured and upgraded with minor and major software upgrades. In virtualization the SLA is typically targeted on the uptime and performance features of the actual VM.

In cloud the focus is extended, from the VM to the whole datacenter. All the datacenter facilities are presented to the user via self-service portals and/or via a application programming interface (API) these services consists of software defined entities that can be fully controlled by it's user without any intervention of IT staff.
The user can create their own datacenter environment based on a predefined budget, the datacenter is implemented automatically using on premises compute, network and storage resources or the user is (seamlessly) connected to resources remotely.

Cloud resources help the user to scale out (use smaller but more compute instances) as the virtual machines themselves cannot/should not be tailored to exact specifications. A cloud vm (instance) receives only the minor, security related, OS updates. Major release upgrades are performed by deleting a instance then redeploy a new instance based on a new OS image.


The SLA in cloud is typically targeted on the IT infrastructure, the ability to start a cloud instance (VM) and use it's datacenter facilities. The uptime of a specific VM should not matter and is normally not part of the Cloud SLA.

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