As part of your continuous deployment process, your application undergoes an I/O load performance test before being deployed to production using new AMIs. The application uses one Amazon Elastic Block Store (EBS) PIOPS volume per instance and requires consistent I/O performance. Which of the following must be carried out to ensure that I/O load performance tests yield the correct results in a repeatable manner?

Answer options:

A.Ensure that the I/O block sizes for the test are randomly selected.
B.Ensure that the Amazon EBS volumes restored from snapshots have been pre-warmed by reading all the blocks before the test.
C.Ensure that snapshots of the Amazon EBS volumes are created as a backup.
D.Ensure that the Amazon EBS volume is encrypted.

Answer – B
During the AMI-creation process, Amazon EC2 creates snapshots of your instance`s root volume and any other EBS volumes attached to your instance.
New EBS volumes receive their maximum performance when they are available and do not require initialization (formerly known as pre-warming). However, storage blocks on volumes restored from snapshots must be initialized (pulled down from Amazon S3 and written to the volume) before you can access the block. This preliminary action takes time and can cause a significant increase in the latency of an I/O operation the first time each block is accessed. For most applications, amortizing this cost over the lifetime of the volume is acceptable.
Option A is invalid because block sizes are predetermined and should not be randomly selected.
Option C is invalid because this is part of continuous integration. Hence volumes can be destroyed after the test, and there should not be snapshots created unnecessarily.
Option D is invalid because the encryption is a security feature and not part of load tests normally.
For more information on EBS initialization, please refer to the below link:
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ebs-initialize.html