1.6 Essential characteristics, and RAS
You can measure a cloud offering against a named checklist instead of a brochure.
Before:00. Groundwork — Linux, Networking & GitUnlocks:02. Compute09. Cost Engineering
The five essential characteristics turn brochure language into a checklist, and RAS — reliability, availability, serviceability — puts numbers where confidence used to be. This topic sits at the end of the definitional run so a cloud offering can be measured rather than admired. It is also where the risks get named honestly: lock-in, egress charges, opacity during an outage, shared fate with your provider. The common confusion is treating availability and reliability as synonyms; a system can fail often and briefly, or rarely and catastrophically, and the two need different defences.
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The five essential characteristics: on-demand self-service, broad network access, resource pooling, rapid elasticity, measured service
The five named characteristics are the standard definition, and they exist so an offering can be measured rather than described. Checking a product against them is a faster judgement than reading its brochure.
RAS — reliability, availability and serviceability — and what each one costs
Reliability, availability and serviceability are three different promises: how rarely it fails, how much of the time it works, and how quickly it can be fixed. Each is bought separately and each has a price.
Where a cloud provider genuinely beats a traditional IT service provider, and the two places it does not
There are places where a large provider genuinely beats a traditional supplier, and two places where it does not. Being able to name both directions is what makes the comparison credible to somebody sceptical.
Risks and challenges named honestly: lock-in, egress, opacity during an outage, and the shared-fate problem
Lock-in, the cost of moving data out, the silence during an outage, and sharing fate with other tenants are the four standing risks. They are named here honestly because every one of them will come up in a real decision.
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