Elastic Fabric Adapter (EFA) Limitations

Correct Answer: B and D.

An Elastic Fabric Adapter (EFA) is a network device that you can attach to your Amazon EC2 instance to accelerate High-Performance Computing (HPC) and machine learning applications.

Option A is incorrect because it is a true feature of EFA.

An EFA is an Elastic Network Adapter (ENA) with added capabilities.

It provides all of the functionality of an ENA, with additional OS-bypass functionality.

Option B is correct because it is one of the limitations of EFA (Elastic Fabric Adapter).

Option C is incorrect because OS-bypass functionality is supported only by EFA.Option D is correct because it is also a limitations.

The OS-bypass capabilities of EFAs are not supported on Windows instances.

If you attach an EFA to a Windows instance, the instance functions as an Elastic Network Adapter, without the added EFA capabilities.

Reference:

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/efa.html

The Elastic Fabric Adapter (EFA) is a network interface for Amazon EC2 instances that provides low-latency, high-bandwidth connectivity between instances. It is designed to provide high-performance networking capabilities for demanding HPC (High-Performance Computing) workloads.

Out of the given options, the correct answer is D - OS-bypass capabilities of EFAs are not supported on Windows instances.

The EFA provides all the functionality of an Elastic Network Adapter (ENA), as mentioned in option A, and also supports OS-bypass functionality, which enables direct communication between the application and the network interface card, bypassing the operating system's networking stack. This provides low-latency communication and high bandwidth between instances, making it an excellent choice for HPC workloads.

Option B is incorrect as it describes a security group configuration and does not relate to any specific limitation of EFA.

Option C is incorrect as it is the opposite of the actual limitation of EFA. EFA supports OS-bypass functionality, while ENA does not.

Option D is the correct answer as EFA OS-bypass capabilities are not supported on Windows instances. This is because Windows OS does not currently provide the required interfaces for EFA to support OS-bypass functionality on Windows instances.

In summary, the correct answer is D - OS-bypass capabilities of EFAs are not supported on Windows instances.