Many more cloudy things popping up everyday... However, it would be good to know the shortcomings of the cloud and related technolgies before jumping onto it like every other chap round the corner...
As rightly pointed out by Gojko Adzic in his excellent post, with cloud platforms all you have is "a bunch of cheap servers with poor IO" .
He also mentions the key constraints of Cloud Deployment
- All cloud servers are equally unreliable
- All servers will be equally impacted by network and IO constraints
- Fundamentally Network is unreliable
- There is no fast shared storage
He mentions some fundamental guidelines while doing cloud deployments
Partition, partition, partition: avoid funnels or single points of failure. Remember that all you have is a bunch of cheap web servers with poor IO. This will prevent bottlenecks and scoring an own-goal by designing a denial of service attack in the system yourself.
Plan on resources not being there for short periods of time. Break the system apart into pieces that work together, but can keep working in isolation at least for several minutes. This will help make the system resilient to networking issues and help with deployment.
Plan on any machine going down at any time. Build in mechanisms for automated recovery and reconfiguration of the cluster. We accept failure in hardware as a fact of life – that’s why people buy database servers with redundant disks and power supplies, and buy them in pairs. Designing applications for cloud deployment simply makes us accept this as a fact with software as well.
