Remove the Elastic IP from the EC2 instance. Set up an Amazon S3 bucket for SFTP file storage. Deploy an AWS Transfer Family server with a public endpoint, reassign the Elastic IP to this new endpoint, and configure it to use the S3 bucket. Migrate all files from the current SFTP server to the S3 bucket.

Detach the Elastic IP from the EC2 instance. Establish an Amazon S3 bucket for SFTP file storage. Launch an AWS Transfer Family server with a VPC-based, internet-facing endpoint, reassign the Elastic IP to this endpoint, apply the security group allowing customer IPs, and link it to the S3 bucket. Transfer all files from the existing SFTP server to the S3 bucket.

Unlink the Elastic IP from the EC2 instance. Create an Amazon EFS file system for SFTP file storage. Define an AWS Fargate task to operate an SFTP server, mounting the EFS file system. Set up a Fargate service with this task and place a Network Load Balancer (NLB) in front, reassigning the Elastic IP to the NLB. Attach the security group allowing customer IPs to the Fargate tasks. Move all files from the current SFTP server to the S3 bucket.

Disassociate the Elastic IP from the EC2 instance. Generate a multi-attach Amazon EBS volume for SFTP file storage. Construct a Network Load Balancer (NLB) with the Elastic IP. Form an Auto Scaling group running SFTP server EC2 instances, configured to attach the multi-attach EBS volume upon launch. Direct the Auto Scaling group to deploy instances behind the NLB and apply the security group allowing customer IPs. Transfer all files from the existing SFTP server to the new multi-attach EBS volume.