Question 1

A financial services company is using RDMA over InfiniBand to accelerate the processing of real-time market data between servers. The application employs zero-copy techniques to avoid unnecessary data copies during communication. However, after switching to this configuration, the company observes that CPU utilization is still relatively high during data transfers, and performance gains are less than expected. What could be the most likely reason for the suboptimal performance?

Options :

A : Zero-copy requires additional software-based data serialization, which increases CPU overhead

B : The InfiniBand adapters are not using DMA (Direct Memory Access) for data transfers

C : The application is not properly registering memory regions for RDMA operations.

D : The zero-copy mechanism only applies to small data transfers, not to larger ones

Answer: C

Question 2

What mechanism is primarily used in InfiniBand networks to control which nodes can join and communicate within a subnet?

Options :

A : InfiniBand relies on the physical topology of the network for access control, where only physically connected devices are able to communicate.

B : InfiniBand uses subnet access codes that must be manually configured on each node to authenticate them within the subnet.

C : Partition Keys (PKeys) are used to create partitions, and nodes are only allowed to communicate if they are assigned the same PKey, providing access control within the subnet.

D : The Subnet Manager uses Service IDs (SIDs) to identify and authenticate nodes, only allowing nodes with authorized SIDs to communicate.

Answer: C

Question 3

Which of the following best describes how RDMA (Remote Direct Memory Access) operations work within the InfiniBand protocol stack?

Options :

A : RDMA bypasses the CPU and operating system on the data path, allowing data to be directly transferred between the memory of two systems, reducing CPU overhead and improving data throughput.

B : RDMA allows memory access directly from one host’s CPU to another host-s memory without any involvement of the memory controller, reducing latency.

C : RDMA only works over the physical layer of the InfiniBand stack and requires additional middleware to handle data transfer at the transport layer.

D : RDMA requires the intervention of the OS kernel in both the sending and receiving systems, as it relies on kernel space memory buffers for transferring data between nodes.

Answer: A

Question 4

You are configuring an InfiniBand fabric to optimize high-throughput, low-latency communication for a large-scale HPC cluster. Which advanced InfiniBand feature allows you to ensure traffic prioritization and reduce congestion for critical workloads?

Options :

A : Multipathing (MPIO)

B : Adaptive Routing (AR)

C : Credit-Based Flow Control

D : Service Level (SL) to Virtual Lane (VL) Mapping

Answer: D

Question 5

You are configuring an InfiniBand-based high-performance computing (HPC) cluster for a scientific simulation workload that requires low latency and high throughput communication between nodes. The application is designed to leverage RDMA (Remote Direct Memory Access) to bypass the CPU and improve data transfer efficiency. You notice that while the latency is low, the throughput is not meeting expected levels. Which of the following is the most effective method to optimize RDMA performance for this application?

Options :

A : Enable CPU coalescing to allow RDMA to use more CPU resources

B : Ensure proper alignment of memory buffers to cache lines.

C : Increase MTU size on InfiniBand network interfaces

D : Disable flow control mechanisms for RDMA transfers

Answer: B