Have you used Google Docs, Dropbox or Adobe Photoshop? If you are, then you are already using cloud-based services. In this video, we are going to look at different realizations of cloud computing, starting with web applications. The simplest realization of cloud computing is web applications. These web applications include Google Docs, Dropbox, QuickBooks, YouTube and so on. These are created using standard technologies from the Worldwide Web including HTML, XML, JavaScript and PHP. Why is it cloud computing? So, in the case of web applications, you have a user who is using his or her own device in order to access these web applications that are hosted by a cloud provider. The cloud provider maintains both the hardware that is the actual hardware for the servers and the software which are the Web Applications that a person can use. The client could use his or her machine in order to access the web applications on the remote servers in the cloud. If the client's machine fails, either because the operating system fails or the hardware fails and if this becomes unavailable, the client could still use this Web applications from another machine. All they have to do is simply move to another machine and use the web application from the other machine. This works because the application is not running on the client's computer. Instead, the application is running on the cloud server. There is a separation of software from the client operating system and hardware. Since the software is running on a remote cloud server, it is separated from the clients operating system and the hardware of the machine that the client is using in order to access those web services. Therefore, there is a clear separation of the software and the operating system and hardware and therefore this is a most basic form of cloud computing. So, next we're going to look at computer clusters. Computer clusters consists of multiple servers possibly with different hardware configurations, which are interconnected to form a cluster. These clusters can be used for either, say for example, Active Directory clusters in order to login employees based on their credentials to the system of an organization or database clusters like SQL database clusters. The related databases in the case of a database cluster, will be replicated and on each of the cluster servers. The cluster servers are going to send the databases to a master database and it will distribute it to other database to have replication of the database and its contents. Now, these clusters are optimized for efficiency through load balancing. What a load balancer does is incoming client requests, will be directed to the server with the lighter load. The load balancer is going to look at the load on different servers and it's going to decide which server to send this request to. That way, it can maintain the similar amount of loads on each of the servers. If one server fails, then the others can continue the work. So, this is allowing for optimized performance through load balancing. For example, if in an active directory cluster, if one of the servers fail, the employees of that organization can still log in with the other servers that are a part of the cluster. This would run without any glitch noticeable to the employees. Why is this an example of cloud computing? Well, this computer clusters allow the separation of apps from hardware using redundancy. As you can see, the application running on top of this computer cluster, whether its SQL database or whether it's Active Directory cluster, whatever that application is, it's separated from the underlying hardware by using replication or redundancy through the bunch of these servers working together in order to provide that service. So, if one fails, the others can take over the job. In the next video, we're going to look at terminal services, application services and hosted instances.