Web datacenters and clusters can be larger than the world’s largest supercomputers,
and run workloads that are at least as heteroge- neous and complex as their
high-performance computing counterparts. And yet little is known about the unique
job scheduling challenges of these environments. This article aims to ameliorate
this situation. It dis- cusses the challenges of running web infrastructure and
describes several techniques to address them. It also presents some of the problems
that remain open in the field.