Which solution meets these requirements MOST cost-effectively?
Provision an enhanced networking optimized EC2 instance to serve as a shared NFS storage system.
Create an Amazon S3 bucket that uses the S3 Standard-Infrequent Access (S3 Standard-IA) storage class. Mount the S3 bucket to the EC2 instances in the Auto Scaling group.
Create an SFTP server endpoint by using AWS Transfer for SFTP and an Amazon S3 bucket. Configure the EC2 instances in the Auto Scaling group to connect to the SFTP server.
Create an Amazon Elastic File System (Amazon EFS) file system that uses the EFS Standard-Infrequent Access (EFS Standard-IA) storage class. Mount the file system to the EC2 instances in the Auto Scaling group.
Explanations:
Provisioning an enhanced networking optimized EC2 instance as a shared NFS storage system would not provide high availability and could lead to a single point of failure. Additionally, it would require significant management overhead, which is not cost-effective compared to managed solutions.
While Amazon S3 with the Standard-IA storage class offers durability and cost-effectiveness for infrequent access, it cannot be mounted directly as a file system. This would require changes to the application to use S3 APIs instead of traditional file system calls, which contradicts the requirement that the application cannot be modified.
Creating an SFTP server using AWS Transfer for SFTP does not align with the requirement for a shared file system. Although S3 can store documents, using SFTP would also require changes to the application and does not provide a seamless file system interface that is necessary for the existing workload.
Creating an Amazon EFS file system provides a highly available and scalable shared file storage solution. EFS can be mounted across multiple EC2 instances and offers seamless integration with the Auto Scaling group, making it ideal for the requirements of maintaining availability and compatibility without needing application modifications.
I appraise that the answer is:
Create an Amazon Elastic File System (Amazon EFS) file system that uses the EFS Standard-Infrequent Access (EFS Standard-IA) storage class. Mount the file system to the EC2 instances in the Auto Scaling group.