3.2 - Virtualisation
What is virtualisation?
Virtualisation describes the creation of a virtual version of a device, software or server.
Storage virtualisation combines multiple storage devices so that they appear to be just one device.
Server virtualisation allows one physical server to host multiple virtual machines, each running separately.
Think back to the hypervisor from 3.1. A virtual client is a full desktop environment where the processing happens remotely. For example, where an operating system is managed and hosted centrally but displayed locally on a different computer (dumb client).
A problem with virtual clients is that users will be unable to work if network connectivity is lost, and an increased load on the server might result in poor performance for each client.
A common use of virtualisation is in testing applications within a secure environment before they are used with the main system.
General Benefits & Drawbacks of Virtualisation
Benefits of virtualisation:
Costs are cheaper in the long-term because money is saved by not purchasing multiple physical devices. Money is also saved due to less cabling and lower power consumption.
If set up efficiently, it can be used for higher performance at a lower cost - "Do more with less".
Programs can be tested in a secure environment before main-system deployment.
Simplified response to recover after a disaster because only the server needs to be fixed.
Drawbacks of virtualisation:
If not set up efficiently, users could face serious performance issues, as fewer servers do more work.
If a single physical system fails, the impact will be greater.
Initial set up is complex, requires technical knowledge and can cost a lot.
Easier for hackers to take more information at once as the data is stored in the same place.
'The cloud' is storage that is accessed through a network, primarily the internet. A cloud server is an example of storage virtualisation as data may be stored across multiple physical devices. There are three different types of cloud storage:
Private cloud is where a business will have its own data centre that can be accessed by employees. This allows for flexible and convenient data storage and gives the business control over data management and security. Users of the private cloud will not usually have to pay individually for access - but the company will need to spend a lot of money on set up and maintenance.
Public cloud uses third-party service providers such as Google Drive or DropBox to provide storage over the internet. Public cloud is usually a pay-for-use service, where businesses will pay for specific amounts that they need. Data management and data security is maintained by the cloud provider and the business is dependent on them providing constant access and deploying effective security measures.
Hybrid cloud uses a mix of on-site storage (private cloud) and third-party (public cloud) services. Organisations can move workloads between private and public clouds as their specific needs and costs change. A benefit of hybrid cloud is that it gives an organisation more flexibility and data storage options. As an example, a company could use on-site or private cloud storage to hold sensitive information and third-party, public cloud services to hold less important data.
3.2 - Virtualisation:
1. What is the difference between server and storage virtualisation? 
2. What is a virtual client? 
3. Explain the advantages and disadvantages of using virtualisation. 
4. Describe the differences between private, public and hybrid cloud storage.