What should be the ratio of Virtualization and Physical server in Linux Environment.?
The short answer is: Whatever is needed by the business/customers.
There is no actual answer to this question. People choose physical, virtual, container, or cloud for all different reasons, but ultimately, it's a selection to support the operations/business/customers. You might choose physical because you need to very closely guard and secure your data, which on-premisis physical hardware makes easy. But to make this decision, you're going to lose portability and take on additional responsibility for things like hardware puchase, management, and maintenance as well as have some responsibility for the hosting of this system and any network, power, cooling requirements it may have.
Alternatively, one could choose cloud because there is no 'hardware' or 'datacenter' to maintain. All you need to do is manage the system. However, that also means that you need to be prepared for when that system vanishes due to a cloud error or outage. Is downtime acceptable, if so, how much? If the machine was to be inadvertantly destroyed, how would you rebuild it? How long would that take, how much of it's data would be lost? Are the hourly run-costs for the system a viable operations expenditure, vs. a hardware purchace and management (a capital expenditure)? Does being in the cloud change the life expectency or management of the system? etc.
Each deployment methodology has pros and cons.