These options are the most suitable ways to design a shared storage solution for a web application that is deployed across multiple Availability Zones and requires strong consistency. Option B uses Amazon Elastic File System (Amazon EFS) as a shared file system that can be mounted on multiple EC2 instances in different Availability Zones. Amazon EFS provides high availability, durability, scalability, and performance for file-based workloads. It also supports strong consistency, which means that any changes made to the file system are immediately visible to all clients. Option E uses Amazon S3 as a shared object store that can store the web content and serve it through Amazon CloudFront, a content delivery network (CDN). Amazon S3 provides high availability, durability, scalability, and performance for object-based workloads. It also supports strong consistency for read-after-write and list operations, which means that any changes made to the objects are immediately visible to all clients. By setting the metadata for the Cache-Control header to no-cache, the web content can be prevented from being cached by the browsers or the CDN edge locations, ensuring that the latest content is always delivered to the users.
Option A is not suitable because using AWS Storage Gateway Volume Gateway as a shared storage solution for a web application is not efficient or scalable. AWS Storage Gateway Volume Gateway is a hybrid cloud storage service that provides block storage volumes that can be mounted on-premises or on EC2 instances as iSCSI devices. It is useful for migrating or backing up data to AWS, but it is not designed for serving web content or providing strong consistency. Moreover, using Volume Gateway would incur additional costs and complexity, and it would not leverage the native AWS storage services.
Option C is not suitable because creating a shared Amazon EBS volume and mounting it on multiple EC2 instances is not possible or reliable. Amazon EBS is a block storage service that provides persistent and high-performance volumes for EC2 instances. However, EBS volumescan only be attached to one EC2 instance at a time, and they are constrained to a single Availability Zone. Therefore, creating a shared EBS volume for a web application that is deployed across multiple Availability Zones is not feasible. Moreover, EBS volumes do not support strong consistency, which means that any changes made to the volume may not be immediately visible to other clients.
Option D is not suitable because using AWS DataSync to perform continuous synchronization of data between EC2 hosts in the Auto Scaling group is not efficient or scalable. AWS DataSync is a data transfer service that helps you move large amounts of data to and from AWS storage services. It is useful for migrating or archiving data, but it is not designed for serving web content or providing strong consistency. Moreover, using DataSync would incur additional costs and complexity, and it would not leverage the native AWS storage services. References:
What Is Amazon Elastic File System?
What Is Amazon Simple Storage Service?
What Is Amazon CloudFront?
What Is AWS Storage Gateway?
What Is Amazon Elastic Block Store?
What Is AWS DataSync?
