Overview of Windows Azure BLOB Storage

Windows Azure has several constituent parts, one of which is BLOB storage. BLOB stands for binary large object and refers to the storage of binary data such as images, videos, and more. BLOB storage is one of three primary types of storage within Windows Azure; the others types are table storage (for non-relational data storage) and queue storage (for messaging). For more information on Windows Azure storage, go to http://www.microsoft.com/windowsazure/storage/default.aspx.

Windows Azure BLOB storage is also a flexible cloud storage option that provides a set of REST-based APIs. By using these APIs, you can interact with the different Windows Azure storage services by using a standard HTTP request. For example, the following REST URI queries BLOB storage and returns an XML feed of all of the images and image properties in the imagefiles BLOB container:

http://fabrikam.blob.core.windows.net/imagefiles?restype=container&comp=list

					  

At a high level, the underlying structure of Windows Azure BLOB storage includes three core resources:

• An account For example, in the following URI, fabrikamlegal represents the account name: http://fabrikamlegal.blob.core.windows.net. (As the owner of the BLOB storage account, you will have an account key that enables you to access it.)

• A container This is the artifact that stores the BLOBs.

• The binary object This represents the underlying file that is stored in the container—for example, imgBoston.jpg.

Each of the above core components is in some way expressed within the REST URI. For example, using the information above, the URI to access the imgBoston.jpg BLOB would look like the following:

http://fabrikamlegal.blob.core.windows.net/mystuff/imgBoston.jpg

In this URI, fabrikamlegal is the account name, mystuff is the container, and imgBoston.jpg is the BLOB.

Note:

More Info For more information about the Windows Azure BLOB REST API, see “Blob Service API” at http://msdn.microsoft.com/en-us/library/dd135733.aspx.

Within BLOB storage, you’re not constrained to the number of BLOBs in a container. For example, you could have one or more BLOBs per container. You can also have many containers within an account; Figure 1 shows one account with three containers, each containing a set of binary files.

When you translate Figure 1 into code, you’ll find that things look a little more complex than this conceptual representation might suggest. For example, if you look at the code snippet that follows, you’ll see that your account information can be derived programmatically from your data connection string settings (DataConnectionString), which is a resource that is automatically created for you when you create the cloud project:

     ...
              //Set up and create BLOB storage containers.
              azureStorageAcct =
                 CloudStorageAccount.FromConfigurationSetting("DataConnectionString");
              azureBlobClient = azureStorageAcct.CreateCloudBlobClient();

              //Create a new container for the images to upload.
              azureBlobContainer = azureBlobClient.GetContainerReference("imagefiles");
              azureBlobContainer.CreateIfNotExist();

              //Set the permissions for the image BLOB container.
              azureBlobPermissions = new BlobContainerPermissions();
              azureBlobPermissions.PublicAccess = BlobContainerPublicAccessType.Container;
              azureBlobContainer.SetPermissions(azureBlobPermissions);
...

					  

You’re not necessarily relegated to using the DataConnectionString property; you can, in some cases, use other methods to map the connection information needed to interact with BLOB storage through other means, such as parsing resource strings. You also see from the code snippet that you can create a new container—in this case, one called imagefiles. You might notice that this code first called the GetContainerReference method, which is then followed by the CreateIfNotExist method. The latter will create a new container called imagefiles if that container does not already exist within the BLOB storage. The final item in the code snippet is the setting of the permissions. Windows Azure has a very flexible system of permissions, enabling you to assign discrete levels of permission for the container or for the BLOB within the container—or even create a sharable key that can expose BLOBs or containers. In the code just shown, you’re assessing public access to the BLOB storage.

It was mentioned earlier that REST is the primary way of integrating with BLOB storage, and this is absolutely true. However, as you can see from the code just examined, you can also use Microsoft .NET Framework libraries. (The .NET Framework libraries are simply .NET wrappers for the REST-based API.)

To create BLOB storage, you need to ensure that you have created a new storage account in your Windows Azure developer portal. After you have created this account, you can then use it for BLOB storage. To create a new storage account, simply navigate to your Windows Azure developer portal, click Hosted Services | Storage Accounts & CDN, click Storage Accounts, and then select New Storage Account in the main UI ribbon. Windows Azure will prompt you to provide a subscription option, account name, and region, and then you can click OK to create the new storage account.