Chapter 6 Warehouse-Scale Computers to Exploit Request-Level and Data-Level Parallelism Topic 4 Storage Prof. Zhang Gang gzhang@tju.edu.cn School of Computer Sci. & Tech. Tianjin University, Tianjin, P. R. China

Storage Storage options: Use disks inside the servers, or Network attached storage (NAS) through Infiniband The NAS solution is generally more expensive per terabyte of storage, but it provides many features, including RAID techniques to improve dependability of the storage WSCs generally rely on local disks

Storage Google File System (GFS) uses local disks and maintains at least three replicas This redundancy covers not just local disk failures, but also power failures to racks and to whole clusters The eventual consistency flexibility of GFS lowers the cost of keeping replicas consistent, which also reduces the network bandwidth requirements of the storage