Warehouse-scale cloud datacenters co-locate workloads with different and often complementary characteristics for improved resource utilization. To better understand the challenges in managing such intricate, heterogeneous workloads while providing quality-assured resource orchestration and user experience, we analyze Alibaba's co-located workload trace, the first publicly available dataset with precise information about the category of each job. Two types of workload - long-running, user-facing, containerized production jobs, and transient, highly dynamic, non-containerized, and non-production batch jobs - are running on a shared cluster of 1313 machines. Through workload characterization, we find evidences that imply that one workload scheduler makes seemingly independent scheduling decisions regardless of the co-existence of the other. This upsurges an imminent need for a more integrated, global coordinating system that transparently connect multiple resource schedulers together and cohesively coordinates the multiple heterogeneous workloads for greater efficiency. Our multifaceted analysis reveals insights that we believe are useful for system designers and IT practitioners working on cluster management systems.