24. Virtualisation & the Cloud

Cloud Computing

Computational paradigm
Out-source your computation and storage needs to a well-managed data centre
No worries about the physical machines: power, cooling, maintenance
Virtualisation provides the necessary isolation to share multiple clients on a single physical machine

Number of characteristics define cloud data, applications services & infrastructure
Remotely hosted - services or data are hosted on remote infrastructure No-need-to-know in terms of the underlying details of infrastructure, application interface with the infrastructure via the APIs
Ubiquitous - services or data are available from anywhere
Flexibility and elastically allow these systems to scale up and down will:
- Utilising resources of all kinds
- CPU, storage, server capacity, load balancing, databases
Commodified - result is utility computing model similar to traditional utilities, like gas and electricity

Easier for IT managers to deal with the computing
Scalability, backups, depreciation, reliability, performance
Rapid elasticity is currently one of the key challenges in cloud computing
Capabilities can be rapidly and elastically provisioned
To the consumer, resources often appear to be unlimited and can be purchased in any quantity at a time
Optimisation of the current usage will save energy!
Prediction techniques may help alleviate the problem based on historical data

Allows to carry out multiple OS and carry out a clever management
Challenge is to move the VM from the hardware that needs servicing to a new machine without taking it down at all
Non-live migration - Instead of shutting down computer, just pause the VM (checkpointing), then copy over the memory pages used by the VM to the new hardware as quickly as possible
Live Migration - Idea is to start moving the virtual machine while it is still operational

Provides resources of the underlying cloud infrastructure to customers
VM's with different OSs and other visualised hardware, processing, storage networks
End-user: typically a system administrator

Provides service in the form of a platform on which the customer's applications can run
Tools to create your own applications
End-user: developers