A Windows file server runs on a fleet of EC2 instances across multiple Availability Zones, but application servers cannot access files concurrently from that fleet. What is the most operationally efficient way to provide concurrent access to the same files for the application servers?

The most operationally efficient solution is to deploy Amazon FSx for Windows File Server in Multi-AZ mode. FSx for Windows File Server provides fully managed, highly available, and scalable file storage that is natively compatible with Windows applications and supports the Server Message Block (SMB) protocol. Multi-AZ deployment ensures high availability and automatic failover, making it ideal for concurrent access from multiple application servers. Creating an Amazon EFS Multi-AZ file system is incorrect because EFS is a Linux-native NFS file system and does not natively support Windows file sharing (SMB) without additional configuration or gateways. Provisioning an EBS volume with Multi-Attach is incorrect because while Multi-Attach allows multiple instances to read/write to the same volume, it's block storage, not a shared file system. It requires a clustered file system (like Windows Server Failover Clustering) to prevent data corruption, which adds significant operational overhead and complexity. Creating two FSx for Windows File Server file systems with DFS replication is less efficient than a single Multi-AZ FSx deployment, as it involves managing replication and potentially more complex client configurations.