Which performance index is most suitable to find out real performance of your VM limited by sharing and quotas?
For example, if you have a physical server with 4 cores and 16 GB RAM, its performance limit might be higher than if you have same on AWS or in some VMWare product.
How to compare to find out the gap? Is there an overall index or better to use some reference applications' performance as benchmark? (tough, though, if you still going to develop that application)
You should do a comparison of commercial virtualization products on the same hardware resources, OR benchmarking commercial virtualization products individually, there are ways to do it, you can even script it.
For example, VMmark is a free tool used to measure the performance and scalability of virtualization platforms VMmark
Since your question is very generic, you should clarify real performance, overall performance. It might mean "real performance in virtualization".
IMHO an absolute benchmark can be rather useless/misleading, I'd always consider the specific context of the application intended to be executed on the platforms being benchmarked and its performance requirements and use only benchmarks relevant to that application context.
A few examples:
if the application doesn't make a lot of use of the CPU and/or its memory, comparing the number of cores and/or the amount of RAM or benchmarking CPU/RAM use would not be very relevant
if the application accesses data on AWS S3 using an AWS platform may provide better performance than using an on-premises bare metal or VMware platform even if the AWS platform's absolute I/O performance is below that of the on-premise platform
Side note: by always starting with the application context in mind potentially more performant solutions other than bare metal/VM/Infrastructure as a Service (IaaS) can be selected, for example Platform as a Service (PaaS) or serverless/Function as a Service (FaaS) solutions. It all depends on the application.
