by Filip
16. May 2010 00:36
After writing about IaaS, PaaS, Saas this week it struck me that there is in fact nothing new in this overview. I said that IaaS delivers a hosted infrastructure, but at least a decade now I can host servers on which I run my own platforms. Similarly hosted web service platforms and database platforms have been available long before the cloud was commonplace. What's new?
Cloud services clearly provide something new compared to the outsourced services we already know, so I've tried to corner what exactly sets them apart. Here's the essential characteristics of a cloud service I came up with:
- Provisioning on-demand. There's no need anymore to wait for the delivery of hardware or the installation of software. The infrastructure is already available, it only needs to be activated. Hence, services are available minutes after you subscribe to them.
- Utility computing. With cloud services you only pay for consumed processor clock cycles, storage, and data transfers. In stead of buying or renting a car, you only pay for the mileage you drive.
This may well be cloud computing's biggest benefit. There's no need to invest in infrastructure to accommodate for periods of peak performance that is sitting idle the rest of the time. When your computing resources cannot handle the workload, you fire up new instances. - Distributed Computing. Both features above are made possible through distributed computing: the execution of a single calculation on multiple computers. When you sign in for a service, a virtual computing instance is set up that runs on multiple physical servers. Probably these servers are distributed geographically to guarantee the availability of your service. When an entire data center goes offline, your service picks up automatically in an alternate location.
There have been times when I would physically visit the rack in the data center of my provider where my hosted IIS or SQL Server was running. Those days are over. There’s no telling where exactly your application is running or your data resides. The only thing you know for sure is that it is somewhere within the data centers of your provider. I think this is why they call it “the cloud”.
If you think of something I forgot, please leave a comment.
23/3/2011: Here are the essential cloud characteristics defined by someone who knows more about it than me. Read Cloud Computing 101. Turns out my definition wasn't so far off after all.