Microsoft's latest Cloud Computing offering is called Azure. (You can sign up for an account here if you want to follow along.) Azure is made up of two different parts: Azure Hosted Services and Azure Storage Accounts. Over the course of these blog posts, we'll be covering both and how to access them using a library that can be used with VS2005 from XP, but we're going to start with a quick overview of Azure Storage Accounts today.
Azure Table Storage (ATS)
Azure Table Storage (ATS) is a slightly misnamed tool. It's really Microsoft's take on a schemaless database. Within your ATS space, you can create "tables", which are really URIs used to access the data. At each of these URIs, you can create Entities, basically XML that is addressable by a PartitionKey and a RowKey. The PartitionKey is a means by which Microsoft determines how best to load balance data across nodes. RowKeys are unique within a PartitionKey. Given that, it can be handy to think of the PartitionKey as a traditional table name and the RowKey as the PrimaryKey, they serve similar functions.
An Entity can contain 252 properties. (MS says it's 255 but they then say that 1 of those must be the PartitionKey, one must be the RowKey and one must be the TimeStamp that you cannot change so it's really 252.) These 252 properties can be defined as different data types but, part of the beauty and pain of schemaless databases is that you can have two Entities on the same partition that define a property named EventDate and have one be string and one be date and that will lead to lots of fun when you go to query data.
But that's ok. SQL Server does a lot of processing for us to ensure that data is consistent. That's good, but not necessarily scalable. Shifting that emphasis from the back end to your front end processor does take more work, but it's far more scalable; a point we'll discuss over the next week.
Azure Blob Storage (ABS)
Azure Blob Storage (ABS) is exactly what it sounds like, a place on the net to store Binary Large Objects. You can create containers, which are URIs used to access the data. These containers can be publicly accessible or not. If it's publicly accessible then it can be accessed like any other item. The image below, for example, is hosted on a public container on ABS.
Azure Queue Storage (AQS)
Azure Queue Storage (AQS) is a communications mechanism that is used to communicate with Azure Hosted Services Worker Roles (which can be considered to be Windows Services). You can create queues that are URIs that can contain messages that store up to 8KB of data to tell the Worker Role what to do. If you need more, you'll need to create an ABS blob that the Worker Role can access.
So, that's the 50,000 foot view of Azure Storage Accounts. Tune in Monday to dig into Azure Storage Account Authentication (it'll be fun, I promise!)