A pharmaceutical company is generating rapidly increasing data volumes. Researchers regularly need a subset of the dataset immediately with minimal lag, while the full dataset does not require daily access. All data currently resides on on-premises storage arrays and the company wants to reduce capital expenses. Which storage solution should a solutions architect recommend?

A Storage Gateway volume gateway with cached volumes is ideal because it stores the full dataset in S3 (reducing capital expenses) while keeping frequently accessed data subsets locally cached for low-latency access. This directly addresses the requirement for immediate access to a subset and less frequent access to the full dataset. AWS DataSync is for one-time or scheduled bulk transfers, not for providing low-latency access to a subset of data on an ongoing basis. A file gateway presents an NFS/SMB interface, which isn't specified as a requirement, and while it uses S3, the volume gateway's cached mode better fits the "subset immediately" and "full dataset not daily" access pattern. EFS is a fully managed NFS file system, but the question implies a need to cache a subset of a larger dataset, which a volume gateway handles more directly and cost-effectively for this specific use case than migrating everything to EFS.