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Overview of Azure Virtual Machines

Updated: March 3, 2015

An Azure virtual machine gives you the flexibility of virtualization without spending the time and money to buy and maintain the hardware that hosts the virtual machine. However, you do need to maintain the virtual machine -- configuring, patching, and maintaining the operating system and any other software that runs on the virtual machine.

  • A virtual machine is a software version of a computer that you configure and maintain according to your needs.

  • An operating system image is a set of one or more files to be used as a template to create a new virtual machine. An image acts like a template because it doesn’t have the personalized settings that a configured virtual machine has, such as the computer name and user account settings.

  • A virtual machine OS disk is virtual hard disk (in .vhd file format) that can be booted and mounted as a running version of an operating system instance. Virtual machines can also use one or more data disks, which can be attached to the virtual machine at any time.

  • An Microsoft Azure application can have multiple virtual machines. All virtual machines that you create in Microsoft Azure can automatically communicate using a private network channel with other virtual machines in the same cloud service or virtual network. Microsoft Azure allows you to load-balance traffic between them.

To find out which Microsoft applications are supported when running in Microsoft Azure Virtual machines, see Microsoft server software support for Azure Virtual Machines.

You can create a virtual machine in Microsoft Azure by using the Azure Management Portal, Azure PowerShell, the programmable API interface (REST); or the command-line tools provided for Mac and Linux desktops.

Regardless of which tool you use, you’ll need to pick an operating system to use with your virtual machine. There are a few ways you can do this:

  • Use an image provided by Azure or a certified partner: You can create your own virtual machine directly in the cloud by using an image provide by Azure or one of its certified partners.

    Use an image based on an Azure VM. To use this approach, you ‘capture’ a running virtual machine, which creates an image file in the same storage account as the operating system disk of the captured virtual machine. You can then use this image to create multiple virtual machines. For instructions, see How to Capture a Windows Virtual Machine to Use as a Template and How to Capture a Linux Virtual Machine to Use as a Template.

  • Use your own image or disk: You can upload your own .vhd file to use as either an image or a disk. The difference is that an image is appropriate to use repeatedly, like a template, and a disk isn’t. For example, if you want to retain specific application settings, such as a SQL Server installation, you can upload the .vhd file as a disk and then create a virtual machine from this disk. For instructions, see Creating and Uploading a Virtual Hard Disk that Contains the Windows Server Operating System.

When you create a virtual machine, choices you’ll need to make include the following:

  • The size of the virtual machine. This determines configuration such as the number of CPU cores, amount of memory, and storage capacity. For details, see Virtual Machine and Cloud Service Sizes for Azure.

  • The operating system. You can choose from stock images, some of which include SQL Server or Sharepoint. Or, if you’ve uploaded your own VHD, you can use that as a custom image for the virtual machine.

  • The networking configuration. If you want a virtual machine to use a virtual network, you’ll need to specify the virtual network when you create the virtual machine. For more information, see the Virtual Network Overview.

  • The cloud service configuration. Each virtual machine resides in a cloud service, either by itself or with other virtual machines. When you place virtual machines in the same cloud service, you can load balance your applications and services by configuring load-balanced endpoints. For instructions, see Load Balancing Virtual Machines

See About Azure VM configuration settings for a summary of the settings and links to details about them.

Microsoft Azure Virtual Network is one of several networking services available in Azure. The following diagram shows how Virtual Network can be used to extend an enterprise network to include Microsoft Azure virtual machines. This brings a great advantage for migrating existing applications to Microsoft Azure. You can easily support hybrid applications that span cloud and on-premises. You can manage your own virtual networks within Microsoft Azure and leverage the hosted VPN gateway to establish connectivity between on-premises and cloud. You can enable virtual machines running in Microsoft Azure to be joined to your corporate domains running on-premises.

As seen in the diagram, within an Microsoft Azure Virtual Network, you can run an Active Directory Domain enabled DNS server in one virtual machine while hosting a SQL Server database in another virtual machine; and your application code can run via a web role managed by Microsoft Azure.

Migration with infrastructure as a service

For more information about networking in Azure, see Network Services. To find out more about Virtual Network, see Virtual Network Overview.

All virtual machines in the same cloud service or virtual network can automatically communicate with each other using a private network channel. However, to communicate with other resources on the Internet or other virtual networks, a virtual machine uses endpoints. These endpoints handle the inbound network traffic to the virtual machine. For instructions, see How to Set Up Endpoints to a Virtual Machine.

Using Microsoft Azure Virtual Machines (Virtual Machines) unblocks development or migration of applications that have dependencies on resources that require virtual machines. You can quickly take advantage of Microsoft Azure by migrating an existing application as-is using Virtual Machines. In addition, you can connect different application models such as Web Sites or Cloud Services web and worker roles with Virtual Machines.

The following application patterns are some examples that can leverage the advantages of the Microsoft Azure Virtual Machines:

  • Existing non-mission critical database applications

  • New database applications to be deployed to SQL Server in Virtual Machines when Microsoft Azure SQL Database does not provide all the necessary features

  • A quick and easy development and test environment for new database applications

  • A backup solution for on-premises database applications

  • A solution that can scale on-demand easily and rapidly at peak times

  • A solution that can overcome virtualization platform inefficiencies on-premises

  • A solution that have dependencies on resources that require virtual machines such as SQL Server, Active Directory, MongoDB, MySQL, or SharePoint.

When you consider migrating on-premises applications to the cloud platform, we recommend that you carefully plan each migration phase. A typical migration project includes Analysis Phase, Application Migration Phase, Data Migration Phase, Testing and Optimization Phase, and Operation and Management Phase. For more information on each phase, see Overview of the Migration Life Cycle in Azure.

We recommend that you move your SQL Server database and data to a virtual machine in Microsoft Azure by using one of the methods described in Migrating to SQL Server in an Azure Virtual Machine. Then, upload and attach a data disk that already contains data to the virtual machine, or attach an empty disk to the machine. You can use the data disks to store the SQL Server logs and data files. See the following tutorials:

The performance of a relational database in Microsoft Azure Virtual Machine depends on many factors, including the VM size, the number and configuration of disks, the network, the configuration of the database software and the application workload. We recommend that developers benchmark their application on several VM sizes and storage configurations to select the most appropriate one. For more considerations, see Performance Best Practices for SQL Server in Azure Virtual Machines. For introductory information, see Getting Started with SQL Server in Azure Virtual Machines.

To provide disaster recovery of data and disks, Microsoft Azure utilizes the recently announced Geo-Replication capability of Microsoft Azure Storage. All changes made by the application or by the customer to the customer-owned operating system disks or data disks are preserved, even in case of a hardware failure, by using Microsoft Azure Blob Storage. As described in the blog post Introducing Geo-replication for Azure Storage, Microsoft Azure Blobs and Tables are replicated between two data centers apart from each other on the same continent, to provide additional data durability in the case of a major disaster, at no additional cost. When you start a virtual machine, Microsoft Azure Storage geo-replication replicates your operating system and data disks to a second geographical region by default.

In addition, make sure that your virtual machines are members of the same availability set. Multiple virtual machines in the same availability set help ensure that your application is available during network failures, local disk hardware failures, and any planned downtime. For details, see Manage the availability of virtual machines.

For information on high availability and disaster recovery techniques when using SQL Server in a Microsoft Azure virtual machine, see High Availability and Disaster Recovery for SQL Server in Azure Virtual Machines.

See Also

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