What is Windows Azure?
The Components of Windows Azure
To understand what Windows Azure offers, it's useful to group its services into distinct categories. Figure 1 shows one way to do this.
Execution Models
One of the most basic things a cloud platform does is execute applications. Windows Azure provides three options for doing this.
Each of these three approaches-Virtual Machines, Web Sites, and Cloud Services-can be used separately. You can also combine them to create an application that uses two or more of these options together.
Virtual Machines
The ability to create a virtual machine on demand, whether from a standard image or from one you supply, can be very useful. Add the ability to pay for this VM by the hour, and it's even more useful. This approach, commonly known as Infrastructure as a Service (IaaS), is what Windows Azure Virtual Machines provides.Web Sites
One of the most common things that people do in the cloud is run web sites and web applications. Windows Azure Virtual Machines allows this, but it still leaves you with the responsibility of administering one or more VMs. What if you just want a web site where somebody else takes care of the administrative work for you?Cloud Services
Suppose you want to build a cloud application that can support lots of simultaneous users, doesn't require much administration, and never goes down. You might be an established software vendor, for example, that's decided to embrace Software as a Service (SaaS) by building a version of one of your applications in the cloud. Or you might be a start-up creating a consumer application that you expect will grow fast. If you're building on Windows Azure, which execution model should you use?Windows Azure Web Sites allows creating this kind of web application, but there are some constraints. You don't have administrative access, for example, which means that you can't install arbitrary software. Windows Azure Virtual Machines gives you lots of flexibility, including administrative access, and you certainly can use it to build a very scalable application, but you'll have to handle many aspects of reliability and administration yourself. What you'd like is an option that gives you the control you need but also handles most of the work required for reliability and administration.
Data Management
Applications need data, and different kinds of applications need different kinds of data. Because of this, Windows Azure provides several different ways to store and manage data.
One of these has already been mentioned: the ability to run SQL Server or another DBMS in a VM created with Windows Azure Virtual Machines. (It's important to realize that this option isn't limited to relational systems; you're also free to run NoSQL technologies such as MongoDB and Cassandra.) Running your own database system is straightforward-it replicates what we're used to in our own datacenters-but it also requires handling the administration of that DBMS. To make life easier, Windows Azure provides three data management options that are largely managed for you.
Each of the three options addresses a different need: relational storage, fast access to potentially large amounts of simple typed data, and unstructured binary storage. In all three cases, data is automatically replicated across three different computers in a Windows Azure datacenter to provide high availability. It's also worth pointing out that all three options can be accessed either by Windows Azure applications or by applications running elsewhere, such as your on-premises datacenter, your laptop, or your phone. And however you apply them, you pay for all Windows Azure data management services based on usage, including a gigabyte-per-month charge for stored data.
SQL Database
For relational storage, Windows Azure provides SQL Database. Formerly called SQL Azure, SQL Database provides all of the key features of a relational database management system, including atomic transactions, concurrent data access by multiple users with data integrity, ANSI SQL queries, and a familiar programming model. Like SQL Server, SQL Database can be accessed using Entity Framework, ADO.NET, JDBC, and other familiar data access technologies. It also supports most of the T-SQL language, along with SQL Server tools such as SQL Server Management Studio. For anybody familiar with SQL Server (or another relational database), using SQL Database is straightforward.Tables
Suppose you want to create a Windows Azure application that needs fast access to typed data, maybe lots of it, but doesn't need to perform complex SQL queries on this data. For example, imagine you're creating a consumer application that needs to store customer profile information for each user. Your app is going to be very popular, so you need to allow for lots of data, but you won't do much with this data beyond storing it, then retrieving it in simple ways. This is exactly the kind of scenario where Windows Azure Tables makes sense.Blobs
The third option for data management, Windows Azure Blobs, is designed to store unstructured binary data. Like Tables, Blobs provides inexpensive storage, and a single blob can be as large as one terabyte. An application that stores video, for example, or backup data or other binary information can use blobs for simple, cheap storage. Windows Azure applications can also use Windows Azure drives, which let blobs provide persistent storage for a Windows file system mounted in a Windows Azure instance. The application sees ordinary Windows files, but the contents are actually stored in a blob.Networking
Windows Azure runs today in several datacenters spread across the United States, Europe, and Asia. When you run an application or store data, you can select one or more of these datacenters to use. You can also connect to these datacenters in various ways:
- You can use Windows Azure Virtual Network to connect your own on-premises local network to a defined set of Windows Azure VMs.
- If your Windows Azure application is running in multiple datacenters, you can use Windows Azure Traffic Manager to route requests from users intelligently across instances of the application.
Virtual Network
One useful way to use a public cloud is to treat it as an extension of your own datacenter. Because you can create VMs on demand, then remove them (and stop paying) when they're no longer needed, you can have computing power only when you want it. And since Windows Azure Virtual Machines lets you can create VMs running SharePoint, Active Directory, and other familiar on-premises software, this approach can work with the applications you already have.Traffic Manager
A Windows Azure application with users in just a single part of the world might run in only one Windows Azure datacenter. An application with users scattered around the world, however, is more likely to run in multiple datacenters, maybe even all of them. In this second situation, you face a problem: How do you intelligently assign users to application instances? Most of the time, you probably want each user to access the datacenter closest to her, since it will likely give her the best response time. But what if that copy of the application is overloaded or unavailable? In this case, it would be nice to route her request automatically to another datacenter. This is exactly what's done by Windows Azure Traffic Manager.Business Analytics
Analyzing data is a fundamental part of how businesses use information technology. A cloud platform provides a pool of on-demand, pay-per-use resources, which makes it a good foundation for this kind of computing. Accordingly, Windows Azure provides two options for business analytics. Figure 5 illustrates the choices.
Analyzing data can take many forms, and so these two options are quite different. It's worth looking at each one separately.
SQL Reporting
One of the most common ways to use stored data is to create reports based on that data. To let you do this with data in SQL Database, Windows Azure provides SQL Reporting. A subset of the reporting services included with SQL Server, SQL Reporting lets you build reporting into applications running on Windows Azure or on premises. The reports you create can be in various formats, including HTML, XML, PDF, Excel, and others, and they can be embedded in applications or viewed via a web browser.Hadoop
For many years, the bulk of data analysis has been done on relational data stored in a data warehouse built with a relational DBMS. This kind of business analytics is still important, and it will be for a long time to come. But what if the data you want to analyze is so big that relational databases just can't handle it? And suppose the data isn't relational? It might be server logs in a datacenter, for example, or historical event data from sensors, or something else. In cases like this, you have what's known as a big data problem. You need another approach.The dominant technology today for analyzing big data is Hadoop. An Apache open source project, this technology stores data using the Hadoop Distributed File System (HDFS), then lets developers create MapReduce jobs to analyze that data. HDFS spreads data across multiple servers, then runs chunks of the MapReduce job on each one, letting the big data be processed in parallel.
Messaging
No matter what it's doing, code frequently needs to interact with other code. In some situations, all that's needed is basic queued messaging. In other cases, more complex interactions are required. Windows Azure provides a few different ways to solve these problems.
Queues
Queuing is a simple idea: One application places a message in a queue, and that message is eventually read by another application. If your application needs just this straightforward service, Windows Azure Queues might be the best choice.One common use of Queues today is to let a web role instance communicate with a worker role instance within the same Cloud Services application. For example, suppose you create a Windows Azure application for video sharing. The application consists of PHP code running in a web role that lets users upload and watch videos, together with a worker role implemented in C# that translates uploaded video into various formats. When a web role instance gets a new video from a user, it can store the video in a blob, then send a message to a worker role via a queue telling it where to find this new video. A worker role instance-it doesn't matter which one-will then read the message from the queue and carry out the required video translations in the background. Structuring an application in this way allows asynchronous processing, and it also makes the application easier to scale, since the number of web role instances and worker role instances can be varied independently.
Service Bus
Whether they run in the cloud, in your data center, on a mobile device, or somewhere else, applications need to interact. The goal of Windows Azure Service Bus is to let applications running pretty much anywhere exchange data.As Figure 6 shows, Service Bus provides a queuing service. This service isn't identical to the Queues just described, however. Unlike Windows Azure Queues, for example, Service Bus provides a publish-and-subscribe mechanism. An application can send messages to a topic, while other applications can create subscriptions to this topic. This allows one-to-many communication among a set of applications, letting the same message be read by multiple recipients. And queuing isn't the only option: Service Bus also allows direct communication through its relay service, providing a secure way to interact through firewalls.
Caching
Applications tend to access the same data over and over. One way to improve performance is to keep a copy of that data closer to the application, minimizing the time needed to retrieve it. Windows Azure provides two different services for doing this: in-memory caching of data used by Windows Azure applications and a content delivery network (CDN) that caches blob data on disk closer to its users.
Caching
Accessing data stored in any of Windows Azure's data management services-SQL Database, Tables, or Blobs-is quite fast. Yet accessing data stored in memory is even faster. Because of this, keeping an in-memory copy of frequently accessed data can improve application performance. You can use Windows Azure's in-memory Caching to do this.CDN
Suppose you need to store blob data that will be accessed by users around the world. Maybe it's a video of the latest World Cup match, for instance, or driver updates, or a popular e-book. Storing a copy of the data in multiple Windows Azure datacenters will help, but if there are lots of users, it's probably not enough. For even better performance, you can use the Windows Azure CDN.Identity
Working with identity is part of most applications. For example, knowing who a user is lets an application decide how it should interact with that user. To help you do this, Microsoft provides Windows Azure Active Directory.
Like most directory services, Windows Azure Active Directory stores information about users and the organizations they belong to. It lets users log in, then supplies them with tokens they can present to applications to prove their identity. It also allows synchronizing user information with Windows Server Active Directory running on premises in your local network. While the mechanisms and data formats used by Windows Azure Active Directory aren’t identical with those used in Windows Server Active Directory, the functions it performs are quite similar.
High-Performance Computing
One of the most attractive ways to use a cloud platform is for high-performance computing (HPC), The essence of HPC is executing code on many machines at the same time. On Windows Azure, this means running many virtual machines simultaneously, all working in parallel to solve some problem. Doing this requires some way to schedule applications, i.e., to distribute their work across these instances. To allow this, Windows Azure provides the HPC Scheduler.
Media
Video makes up a large part of Internet traffic today, and that percentage will be even larger tomorrow. Yet providing video on the web isn't simple. There are lots of variables, such as the encoding algorithm and the display resolution of the user's screen. Video also tends to have bursts in demand, like a Saturday night spike when lots of people decide they'd like to watch an online movie.
Given its popularity, it's a safe bet that many new applications will be created that use video. Yet all of them will need to solve some of the same problems, and making each one solve those problems on its own makes no sense. A better approach is to create a platform that provides common solutions for many applications to use. And building this platform in the cloud has some clear advantages. It can be broadly available on a pay-as-you-go basis, and it can also handle the variability in demand that video applications often face.
Windows Azure Media Services addresses this problem. It provides a set of cloud components that make life easier for people creating and running applications using video and other media.
As the figure shows, Media Services provides a set of components for applications that work with video and other media. For example, it includes a media ingest component to upload video into Media Services (where it's stored in Windows Azure Blobs), an encoding component that supports various video and audio formats, a content protection component that provides digital rights management, a component for inserting ads into a video stream, components for streaming, and more. Microsoft partners can also provide components for the platform, then have Microsoft distribute those components and bill on their behalf.
Commerce
The rise of Software as a Service is transforming how we create applications. It's also transforming how we sell applications. Since a SaaS application lives in the cloud, it makes sense that its potential customers should look for solutions online. And this change applies to data as well as to applications. Why shouldn't people look to the cloud for commercially available datasets? Microsoft addresses both of these concerns with Windows Azure Marketplace, illustrated in Figure 9.
Potential customers can search the Marketplace to find Windows Azure applications that meet their needs, then sign up to use them either through the application's creator or directly through the Marketplace. Customers can search the Marketplace for commercial datasets as well, including demographic data, financial data, geographic data, and more. When they find something they like, they can access it either from the vendor or directly through the Marketplace. Applications can also use the Bing Search API through the Marketplace, giving them access to the results of web searches.
SDKs
Back in 2008, the very first pre-release version of Windows Azure supported only .NET development. Today, however, you can create Windows Azure applications in pretty much any language. Microsoft currently provides language-specific SDKs for .NET, Java, PHP, Node.js, and Python. There's also a general Windows Azure SDK that provides basic support for any language, such as C++.
These SDKs help you build, deploy, and manage Windows Azure applications. They're available either from www.windowsazure.com or GitHub, and they can be used with Visual Studio and Eclipse. Windows Azure also offers command line tools that developers can use with any editor or development environment, including tools for deploying applications to Windows Azure from Linux and Macintosh systems.
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