Nutanix Certified Associate Practice Exam

Which issue could explain lower performance on iSCSI attached virtual disks compared to directly attached disks?

1. The VM's iSCSI traffic is being routed to the data services IP subnet.

2. The performance test is generating small block random I/O.

3. Data Locality ensures that VM attached disks are always faster than iSCSI volumes.

4. The cluster data services IP address is a bottleneck due to shared traffic.

The correct answer is: The cluster data services IP address is a bottleneck due to shared traffic.

The correct answer highlights a significant performance consideration when utilizing iSCSI attached virtual disks. In environments where iSCSI is used, data traffic typically traverses the network, and if the cluster data services IP address is experiencing high volumes of shared traffic, it can become a bottleneck. This congestion can lead to increased latency and reduced throughput for iSCSI communication, impacting overall performance negatively. In contrast, directly attached disks do not rely on network infrastructure for data transfer; thus, they typically offer lower latency and higher throughput. By understanding that shared traffic can lead to bottlenecks, one can recognize the challenges that iSCSI implementations may face under heavy load conditions. Attention to network architecture, data locality, and proper resource allocation is crucial in optimizing performance in scenarios where virtual machines rely on iSCSI for storage.