This paper presents Cluster-Aware Remote Disks (CARDs), a Single System I/O architecture for cluster computing that virtualizes access to remote cluster disks over a System Area Network. CARDs employ cooperative caching policies where all CARDs managing a given disk use a common policy independently of other CARD sets, and the paper describes a decentralized caching policy called Home-based Serverless Cooperative Caching (HSCC) that was implemented. Evaluation showed cache hit ratios over 50% for workloads beyond global cache limits and speedups of up to 1.54 for CARDs over a remote disk interface.