Q31. List the available Virtual Machine sizes in Azure?

Windows Azure provides four VM sizes to the developer to choose from. This enables developers to choose a suitable virtual machine size to run their applications. The billing charges vary depending on the virtual machine size. Depending on the complexity of the application and resource requirements developers can decide the VM sizes. The options are:

virtual machine sizes

Depending on the size of the role we choose, the number of CPU cores, the memory capacity, and the local file system size is allocated to the instance. For example, if we choose extra small compute instance size, the VMs share a single core processor. When we choose higher compute instance sizes, each VM instance will have a dedicated core.

Choosing the right size of the role instances is not a perfect science. It is a trade-off between the performance of an application and the costs we will have to pay. A general advice is to use many small instances instead of few large instances. An application with more number of small instances is resilient to failure. Remember, Azure forces you to sign up a minimum of two instances for each role. You can configure the roles for a Windows Azure Application with Visual Studio.

In the properties window, you can choose the VM size and the number of instances. You can also set the disk space required for the local storage. After we set the role properties, the ServiceDefinition.csdef file contains the settings we have done.

We can locate ServiceDefinition.csdef file in the solution explorer. We can also specify the VM size directly in this file.

Important words:

Number of CPU cores

The earlier generation of a CPU had a single processing unit. The processing unit is also called the core. Today’s generation of CPUs have multiple cores and the number of cores determines the processing power of the computer. The size of the VM is also determined by the number of cores it has and the cost is also determined by the number of cores. Common sizes are single-core, dual-core, four-core and eight-core. In the above table, Compute instance is the VM instance.

Memory capacity

Each compute instance has its own memory capacity which is the working memory which is the key factor which determines the performance of the cloud application.

Local file system

We are familiar with the file system in windows. The windows OS stores all the files based on a predefined file system. We are also familiar with the concept of directories and files. Directories determine the hierarchy of grouping of files whereas files are collection of related data. In the windows file system, there is the concept of volume which many of you may not be familiar. A volume is a grouping of directories and files which reside under the directories.