Exam AWS Certified SysOps Administrator - Associate topic 1 question 262 discussion

For starters, I believe it's a very tricky question and unclear. Although A looks plausible, I believe the right answer is C. In the question it says "A SysOps administrator needs to create alerts that are based on the read and write metrics of Amazon Elastic Block Store (Amazon EBS) volumes that are attached to an Amazon EC2 instance." The key take away here is "EBS volumes". DiskReadBytes, DiskWriteBytes refer to instance store volumes (see, https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/viewing_metrics_with_cloudwatch.html). Instance store volumes are physically attached disks and not EBS volumes (which are network attached drives). Thus, the metrics we monitor look wrong to me. Also, looks like that the metrics we want to monitor are VolumeReadBytes & VolumeWriteBytes. These metrics are included in the AWS/EBS namespace (so it's definitely not D) by default and the CloudWatch agent is not required to monitor them. Finally, SSM agent is irrelevant in this case.

I vote (A) - Installing the Cloudwatch Agent, allows us to collect custom metrics that are not collected by default. Why not D ? Because the "DiskReadBytes" and "DiskWriteBytes" metrics already exist in Cloudwatch and do not require any reconfiguration. https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/viewing_metrics_with_cloudwatch.html

https://aws.amazon.com/pt/blogs/mt/how-to-set-up-amazon-cloudwatch-alarms-to-monitor-io-metrics-of-aws-ebs-volumes-performance-using-metric-math/ C

CloudWatch can monitor I/O based on an entire EBS volume without the agent using the VolumeWriteBytes metric. The question is asking about "volume metrics". If the question were asking about alerting for used or free space in a file system on a volume, then you'd need the CloudWatch agent running on the OS to analyze things from the OS perspective, including I/O with the DiskWriteBytes metric. The VolumeWriteBytes and DiskWriteBytes metrics are basically looking for the same thing. It's like looking at a bucket from the inside or the outside to see what size it is. Both work. If you want to see inside of the bucket or what else is inside the bucket, then you, you need CloudWatch agent running on OS.

The CloudWatch alarms are based on the DiskReadBytes metric and the DiskWriteBytes metric, which are not valid metrics for EBS volumes. The correct metrics for monitoring EBS volumes are the VolumeReadBytes metric and the VolumeWriteBytes metric. Therefore, option C is the correct solution. Option A is incorrect because installing and configuring the CloudWatch agent will not fix the issue. The CloudWatch agent only captures EC2 instance metrics, not EBS volume metrics.

A. The question states "a custom monitoring tool has been installed", therefore the Cloudwatch agent has not been installed and is required to send the metrics.