Exam AWS Certified Solutions Architect - Professional topic 1 question 501 discussion

D : A instance can me moved to placement group

A You cannot move an existing instance into a placement group. Instances within a placement group generally have both a public and a private IP address. Communications across a public IP address are limited to 5Gbps or less. Low-latency, high-throughput communications between placement group members can only occur across the private interfaces, using the private IP addresses. These communications can be either 10Gbps or 20Gbps, and are limited by the instance's network configuration. https://awsinsider.net/articles/2017/06/12/ec2-placement-groups.aspx

Why is it assumed here that the control instance is owned by the same account as the account where the placement group is in? D is incorrect.

Answer id D clearly mention in AWS docs only missing piece in answer is stopping the instance

D - Looks to be the best option To move an instance to a placement group using the AWS CLI Stop the instance using the stop-instances command. Use the modify-instance-placement command and specify the name of the placement group to which to move the instance. aws ec2 modify-instance-placement --instance-id i-0123a456700123456 --group-name MySpreadGroup Start the instance using the start-instances command. https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html#change-instance-placement-group\

I think it's A. Instance can't be moved live. I also sow this question in udemy and the answer is the same.

D. Yes you can't move existing instance to placement group without a down time. But question did not mention there should not be disruption so D is okay.

D. directly from jon bonso's exam

the answer is D. Although like many have said the instance needs to be stopped first

Answer is "A": Terminate and relaunch

To optimize performance on the control instance need to move it into the placement group. For elimination: A - The question does not state if its the same region, I would assume it is - if so, no need to terminate the instance just to stop and modify it and re-start it. B- It can help but i assume the instances are already communication with a private since the cluster instances dont have one. C - It would help but cant reach 20GBs so answer is D - The best way is to migrate the instance inside the cluster placement group - stop it - run the modify CLI command and start it. https://docs.aws.amazon.com/cli/latest/reference/ec2/modify-instance-placement.html https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html#change-instance-placement-group

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html#change-instance-placement-group Why NOT A: “ Before you move or remove the instance, the instance must be in the stopped state. “ Termination in AWS has different results than Stop. “ The key difference between stopping and terminating an instance is that the attached bootable EBS volume will not be deleted. The data on your EBS volume will remain after stopping while all information on the local (ephemeral) hard drive will be lost as usual. “

D. Based on the following: To move an instance to a placement group using the AWS CLI Stop the instance using the stop-instances command. Use the modify-instance-placement command and specify the name of the placement group to which to move the instance. ... Start the instance using the start-instances command

How can we enhance performance? A. Terminate the control instance and relaunch it in the placement group. - Stopping helps changing the placement group. Hence, not needed. B. Ensure that the instances are communicating using their private IP addresses. - There is no Throughput level difference between them C. Ensure that the control instance is using an Elastic Network Adapter. - It is only helpful is instance is in cluster placement D. Move the control instance inside the placement group. - Seems best option. But we need to stop & move - this is not mentioned and so, I will go with A. They have also given hint that AMI is same & hence, termination & recreation seem to help.

D. Here though put is the issue. So no need to chnage IP. We have to change the placement group A is incorrect , because we can stop the instance and move placement group. No need to terminate

D - https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html#:~:text=Before%20you%20move%20or%20remove%20the%20instance%2C%20the%20instance%20must%20be%20in%20the%20stopped%20state.

D. Move the control instance inside the placement group.