Current cloud providers mostly adopt the microservice architecture for latency-critical (LC) services, while co-locating the Best-Effort (BE) tasks like big data analytics to improve the resource utilization of datacenters. Meanwhile, datacenters are evolving toward the disaggregated architecture, in which the compute cluster offers strong computing capabilities while the storage cluster is closer to data storage. Current works partition computing resources for the LC and BEs, to improve the execution performance of BEs while ensuring the Quality-of-Service (QoS) of the LC. However, without appropriate deployment between disaggregated clusters, they result in increased JCT of BE tasks. We propose Comber, a deployment system that reduces BE job completion time (JCT) while ensuring microservice QoS in disaggregated datacenters. Comber consists of a BE task placer and a microservice distributor. Experiments show it reduces BE JCT by 72.4% on average compared to state-of-the-art methods.