Amazon Glacier is designed specifically for long-term archival needs and is the most cost-effective option for storing data for extended periods. It provides secure and durable storage with flexible retrieval times that can range from minutes with expedited retrieval to hours with standard retrieval, making it ideal for archival purposes. Amazon S3 is better suited for general object storage with immediate access, rather than long-term archiving. Amazon EBS is intended for block-level storage volumes for use with EC2 instances and does not fit the archival use case. While AWS Backup is a tool to automate and manage backups for AWS services, it is not a storage service and thus not suitable for archival storage.