Availability of cloud services

Posted: 11.2.2013 in Cloud
Tags: , , ,

Cloud computing combines many different quality aspects. Testing the service is mix of real testing and risk assessment. Risk assessment on the other hand requires wide knowledge from business processes to development processes (like ISO-12207, CMMi) and IT service processes (like ITIL). They also need at least some knowledge about local privacy laws. This post is about availability and its aspects.

Availability is defined at ITIL terminology. It is “Ability of … IT Service to perform its agreed Function when required.” [1] When we start to analyze availability of cloud service, we must understand who the users are and how they are connected to Internet. If the server is at our own computer room, or at well-defined location of service provider, we have clear understanding what parts the network infrastructure has. But as soon as we start to use some cloud service, we lose understanding how the data is flowing between services. In worst case we don’t have any control to data. And even in best case we know the approximate location of our data.

Negative risks have multiple parts. First are our organization and its connection to outside world. If most of the users are using the service from office, the Internet connection from the office to outside world is first possible failure point. When decision for cloud use is done, organization should make sure that their Internet access is enough for required bandwidth. At the same time the business should make decision how long the service can be unreachable.

Service level agreement (SLA) is important part of availability. Unfortunately many cloud service providers are not providing SLA. Their license agreement can state “best industry efforts to guarantee availability” or “99% availability”. The contract usually doesn’t provide much compensate from down time. At the end IT service provider cannot create the SLA when service fails. It can only define, that it takes contact to cloud service provider and notifies them about problems. Then it’s up to cloud service provider how quickly they react.

Cloud computing has also positive sides. Let’s take an example from this blog. I used to host this at one virtual host which was running also other services. It’s at Finland because majority of users for those other services are in Finland. This blog is international blog, so keeping this at Finnish site isn’t mandatory anymore. The major risk at that Finnish site is that if it goes down for any reason, I don’t notice it before morning.

[1] http://www.knowledgetransfer.net/dictionary/ITIL/en/Availability.htm

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