It was suggested that the real test should be "put the new code on the Google cluster and see if the Internet breaks."
There are two fundamental types of workload at Google. "Shared" workloads work like classic mainframe batch jobs, contending for resources while the system tries to isolate them from each other. "Dedicated workloads" are the ones which actually make money for Google - indexing, searching, and such - and are very sensitive to performance degradation. ...The workloads exhibit a lot of big, sequential writes and smaller, random reads. Disk I/O latencies matter a lot for dedicated workloads; 15ms latencies can cause phone calls to the development group.