Use the Windows Azure CDN for Assets

The most common response to running stuff in the cloud (Azure, Amazon in particular) is the that it’s too expensive for the little guy.   And generally, hosting VMs when a small shared site of something similar will suffice is a tough argument.

There are aspects to Azure, though, that are very cost effective as they do “micro-scale” very well.  A good example of this is the Azure CDN, or more simply, Azure Blob Storage.   It’s effective to exchange files, it’s effective at fast delivery, and even lightweight security using shared access signatures (links that essentially only work for a period of time).    It’s durable:  not just redundant internally, but externally as well, automatically creating a backup in another datacenter.

For MSDN subscribers, you already have Azure benefits, but even going out of pocket on Blob storage isn’t likely to set you back much:  $0.15/GB of storage per month, $0.01/10,000 transactions, and $0.15/GB outbound bandwidth ($0.20 in Asia; all inbound free).  A transaction is essentially a “hit” on a resource, so each time someone downloads, say, an image file, it’s bandwidth + 1 transaction. 

Because these are micro transactions, for small apps, personal use, etc., it’s quite economical … often adding up to pennies per month.   A few typical examples are using storage to host files for a website, serve content to mobile devices, and to simply offload resources (images/JS files) from website code.

Depending on usage, the Azure Content Delivery Network (CDN) can be a great way to enhance the user experience.  It may not always be the case (and I’ll explain why) but essentially, the CDN has dozens of edge servers around the world.  While your storage account is served from a single datacenter, having the data on the edge servers greatly enhances speed.   Suppose an app on a phone is retrieving documents/text to a worldwide audience … enabling CDN puts the content much closer. 

I created a test storage account in North Europe (one of the Azure datacenters) to test this, using a small graphic from RPA:  http://somedemoaccount.blob.core.windows.net/images/dicelogo.png

Here’s the same element via the CDN (we could be using custom DNS names, but for demo purposes we’re not): http://az32338.vo.msecnd.net/images/dicelogo.png

Here’s a trace to the storage account in the datacenter – from North Carolina, really not that bad all things considered:

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You can see we’re routed to NY, then on across the pond, and total latency of about 116ms.   And now the CDN:

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MUCH faster, chosen not only by physical distance but also network congestion.   Of course, I won’t see a 100ms difference between the two, but if you’re serving up large documents/images, multiple images, or streaming content, the difference will be noticeable. 

imageIf you’re new to Azure and have an account, creating a storage account from the dashboard is easy.   You’d just click on your storage accounts, and enter a name/location:

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You’d typically pick someplace close to you or where most of your users are.   To enable CDN, you’d just click the CDN link on the left nav, and enable it:

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Once complete, you’ll see if on the main account screen with the HTTP endpoint:

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So why wouldn’t you do this?

Well, it’s all about cacheability.   If an asset is frequently changing or infrequently used, it’s not a good candidate for caching.   If there is a cache miss at a CDN endpoint, the CDN will retrieve the asset from the base storage account.  This will incur an additional transaction, but more importantly it’s slower than if the user just went straight to the storage account.  So depending on usage, it may or may not be beneficial. 

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