Poly Cloud is not multi-cloud. In Poly cloud strategy, we can run specific parts of workloads on different providers for that function only. Poly cloud is a newer strategy which is practical with the advent of serverless and FaaS. One decade back, we had only IaaS, PaaS and SaaS as cloud computing service models.
Poly cloudd is a simple concept and many of using it in some way. Instead of using all the services from a single cloud vendor, we use different cloud providers for different reasons. WordPress plugin to analyze post emotion uses the AI service of IBM Watson. When we are not hosted on IBM, this usage is a basic example of poly cloud strategy. Poly cloud has emerged because of the practical need of today. There are certain differences between each cloud solution provider not only by cost but also for specialization. Polyclad sounds like the description of cloud agnosticism with many similarities. Essentially, cloud agnosticism is for assessing the portability across different cloud solutions. In a multi-cloud approach, we run the same workload on different vendors, but in the poly cloud approach, we decouple the services.
Poly cloud approach also provides a recovery option in case of disasters. Using multiple cloud providers is superior to using all the services from a single provider. This helps us to customize our environment to easily reach our objectives.
As for the conclusion, the best cloud strategy depends on the objectives. Using different cloud vendors may increase the latency, outage of a vendor may create malfunction of the application. It is complex to manage a poly cloud approach not only for different accounts but also for increasing complexity in coding. A minor change in API or policy of one provider may need to completely recode. There are various advantages and disadvantages of mixing the services from different providers. We should think about the return of investment and complexities facing the disasters.