Based on the above output, which of the following BEST describes the root cause?

An administrator is trying to diagnose a performance issue and is reviewing the following output:

System Properties:

CPU: 4 vCPU

Memory: 40GB

Disk maximum IOPS: 690

Disk maximum throughput: 44Mbps | 44000Kbps

Based on the above output, which of the following BEST describes the root cause?
A . The system has reached its maximum IOPS, causing the system to be slow.
B . The system has reached its maximum permitted throughput, therefore iowait is increasing.
C . The system is mostly idle, therefore the iowait is high.
D . The system has a partitioned disk, which causes the IOPS to be doubled.

View Answer

Answer: B

Explanation:

The system has reached its maximum permitted throughput, therefore iowait is increasing. The output of iostat -x shows that the device sda has an average throughput of 44.01 MB/s, which is equal to the disk maximum throughput of 44 Mbps. The output also shows that the device sda has an average iowait of 99.99%, which means that the CPU is waiting for the disk to complete the I/O requests. This indicates that the disk is the bottleneck and the system is slow due to the high iowait. The other options are incorrect because they are not supported by the outputs. The system has not reached its maximum IOPS, as the device sda has an average IOPS of 563.50, which is lower than the disk maximum IOPS of 690. The system is not mostly idle, as the output of top shows that the CPU is 100% busy. The system does not have a partitioned disk, as the output of lsblk shows that the device sda has only one partition sda1.

Reference: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 17: Optimizing Linux Systems, pages 513-514.