VDMig: An Adaptive Virtual Disk Migration Scheme for Cloud Block Storage System

In modern cloud block storage systems, the routing layer bears the task of slicing and distributing application requests to the underlying storage engine and thus becomes the critical path. However, skewed application traffic leads to load imbalance among routing servers, causing severe performance bottlenecks and hurting the quality of service. Existing load balancing methods typically employ static allocation strategies without considering the access pattern of individual virtual disks. They are not well suited to deal with the highly dynamic loads in production. In this paper, we first collect and analyze 7-day workload traces of 130k virtual disks from a commercial cloud block storage system. Based on several observations, we propose VDMig, an adaptive virtual disk migration scheme. VDMig initially divides virtual disks into two types of access patterns, then uses application-level semantics to characterize the load of virtual disks, and finally implements predictive migrating strategies adaptively to achieve dynamic load balancing. Extensive experiments demonstrate that VDMig can achieve fine-grained virtual disk management, effectively balancing the load among routing servers. Compared to the static methods widely deployed in the industry, VDMig can reduce the imbalance by 82.38 % on average.