A company requires a highly available, scalable storage solution that functions as a file system, can be mounted by multiple Linux instances in AWS and on premises via native protocols, and has no minimum size. The company has a Site-to-Site VPN between its data center and its VPC. Which storage solution meets these requirements?

Amazon EFS with multiple mount targets is the correct solution because it provides a highly available, scalable file system that can be mounted by multiple Linux instances both within AWS and on-premises via native NFS protocol, leveraging the existing Site-to-Site VPN. EFS has no minimum size and scales automatically. Amazon FSx Multi-AZ deployments are not suitable because FSx for Lustre or Windows File Server are not native Linux file systems and wouldn't be mounted via native protocols by Linux instances. Amazon EBS Multi-Attach volumes are block storage, not file storage, and cannot be mounted by multiple instances simultaneously as a file system, nor can they be accessed from on-premises. A single EFS mount target with multiple access points still limits the on-premises access to a single endpoint within AWS, which doesn't fully leverage the distributed nature for high availability and performance across multiple on-premises connections.