cloud computing capabilities
What Cloud APIs Show Us About the Emerging Cloud Market
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BuzzBy John Considine
While there is no “official” definition of cloud computing, I believe programmatic access to virtually unlimited network, compute, and storage resources is an essential characteristic. Even though many users access cloud computing through consoles and third-party applications, the foundation of a cloud is a solid Application Programming Interface (API).
Since CloudSwitch works with many cloud providers, we have the opportunity to interact with a variety of cloud APIs—both active and soon-to-be-released versions. After working closely with both the APIs and those implementing them, I’d like to share some impressions:
- Despite all the discussion about standards, clouds are still very different. The important takeaway here is that cloud APIs have to cover a lot more than start/stop/delete a server, and once the API crosses into provisioning the infrastructure (network ranges, storage capacity, geography, accounts, etc.), things get more interesting.
- A cloud requires a very strong infrastructure to work properly. For public clouds, the infrastructure needs to be good enough to sell to others. If you know what to look for, key elements of the cloud API can inform you about the infrastructure, what tradeoffs the cloud provider has made, and the impact for end users (More on this later.)
- The cloud capabilities, and thus the APIs, are evolving fast. We see new API calls and expansion of existing functions as cloud providers add new features and capabilities. At the same time, we are talking with cloud providers about services that are coming soon and what form their API is likely to take. This is a great place to leverage the experience and work of companies like CloudSwitch to integrate the new capabilities into a coherent data model, and keep up with the changes.
An API can give a good indication of what is going on inside the cloud, particularly when you look at the functions beyond simple virtual machine control. I like to look at the network and storage APIs to understand how the cloud is built. For instance, in Amazon, the base network design is that each virtual server receives both a public and private IP addresses. The addresses are assigned from a pool based on where your machine ends up within their infrastructure so that the cloud provider can route network traffic to your servers. In Amazon, the base network design gives each machine both a public and private IP address, which are assigned from a pool based on where your machine ends up within their infrastructure. However, even though you get two IP addresses, the public one is actually just routed (or more accurately NAT’ed) to the private address. In Amazon, you only have a single network interface to your server, which is a simple and scalable architecture for the cloud provider to support, but will cause problems for applications that require at least two NICs (like some cluster applications).
An interesting contrast to this design is found in Terremark’s cloud offering. Like Amazon, IP addresses are defined by the provider so they can route traffic to your servers, but instead of the generic pool of addresses used by Amazon, Terremark allocates a range for your use when you first sign up. The good side of this approach is better control of the assignment of networking addresses; the bad side is potential scaling issues since you only have a limited number of addresses to work with. In addition, you can assign up to four NIC’s to each server in Terremark’s Enterprise cloud, which lets you create more complex network topologies and support applications that require multiple networks for proper operation.
Just when you thought this all makes sense, you have to take into account that in the Terremark model, servers only have internal addresses. Unlike Amazon, there is no default public NAT address for each server. Rather, Terremark has created a front-end load balancer that can be used to connect a public IP address to a specified set of servers by protocol and port. For each protocol and port you want to connect to your server, you must first create an “Internet Service” (in Terremark language) that defines a public IP/Port/Protocol and then assign a server and port to the Service, this creating a connection. Since this is a load balancer, you can add more than one server to each public IP/Port/Protocol group. Now that we have opened the discussion on load balancers, I have to mention that Amazon has a load balancer function as well. And while it is not required to connect public addresses to your cloud servers, it does support connecting multiple servers to a single public IP address.
The key point is that the APIs and the feature sets they define tell a story about the capabilities and design of a cloud infrastructure. Decisions made at the infrastructure level—like network address allocation, virtual device support, and load balancers—will impact the end user features, flexibility, and scalability of the whole service. When considering what cloud environment is best for your applications, you need to look down to the API level to understand how the cloud providers’ infrastructure decisions will impact your deployments.
Building a cloud is clearly complicated—but it provides an unbelievably powerful resource when it’s done right. Cloud providers choose key components and a base architecture for their service which results in clouds with different “sweet spots”. With CloudSwitch, you can span these different clouds and put the right application in the right environment.
