3.2 - Virtualisation
Exam Board:
OCR
Specification:
2016 - Unit 1
What is virtualisation?
Virtualisation is the creation of a virtual version of a device, software, operating system or server. These virtual versions can then be run on a different physical computer system, such as a powerful server.
​
There are many different types of virtualisation.
Storage virtualisation combines multiple separate storage devices into acting and appearing like a single, central storage system.
​
Using storage virtualisation improves scalability as further devices can join the storage system if more space is required. It also simplifies the management of storage across the network.
Server virtualisation allows one physical server to be divided into and host multiple virtual servers, each running separately.
​
Each virtual server operates independently, handling its own operating system and applications. This allows for resources to be used more effectively and improves the scalability and versatility of the physical server.
Client Virtualisation (Virtual Clients)
Client virtualisation is when several virtual desktops are run on a single server - 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. These are often known as 'dumb clients' because the server does the processing for it, meaning it can have minimal resources like a slow processor and little memory / storage.
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.
​​Benefits of client virtualisation:
-
All data is stored in one central location, making backup and disaster planning easier to manage.
-
The whole system can be managed, secured and updated from the server, rather than from each individual system.
-
Hardware costs will be reduced because the virtual clients do not store or process their own data, meaning they can be of a low spec.
-
Users can have multiple virtual machines and log in remotely (from anywhere with internet access).
​
Drawbacks of client virtualisation:
-
Users will be unable to work if network connectivity is lost.
-
There is a high strain on the server as the virtual clients do not store or process data themselves.
-
An increased load on the server might result in poor performance for each client, especially with multiple connections.
-
As the data is stored in one location, there are security risks of unauthorised access if the server is not adequately protected.

Server

Virtual Clients
Cloud Technology
'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 employees can access. 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 greater 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.

Questo's Questions
3.2 - Virtualisation:
1. What is the difference between server and storage virtualisation? [2]
​
2a. What is a virtual client? [1]
2b. What are the advantages and disadvantages of client virtualisation? [8]
​​
3. Explain any further general advantages and disadvantages of using virtualisation, not covered in your answer to 2b. [4]
​​
4. Describe the differences between private, public and hybrid cloud storage. [6]