Xtream: A Production-Level VM Cross-Cloud Disk Migration System with Stripe-Oriented Prefetching

Abstract

Virtual machine (VM) cross-cloud migration refers to the transfer of VMs between different cloud environments, enabling users to deploy their business with greater flexibility. However, VM cross-cloud migration faces many challenges in production due to the high latency and limited bandwidth of cross-cloud networks. These challenges are pronounced in disk migrations, where poor I/O performance persists and significantly constrains the migration process, even leads to migration failures. This drives the demand for VM migration drills, but existing solutions fail to effectively address it. We present Xtream, a production-level cross-cloud disk streaming migration system. By analyzing the business disk I/O patterns, we identify a macro-level locality pattern, characterized as multi-stripe disk access pattern, and develop a stripe-oriented prefetching algorithm in Xtream to improve I/O hit rate. Xtream designs a mechanism for collaborative cold and hot data migration to ensure timely responses to VM I/O requests. The evaluation demonstrates that Xtream reduces I/O latency by 88.2%, shortens cross-cloud VM startup time by 77.7%, and maintains an over 95% disk hit rate during migration, compared to the state-of-the-art streaming migration. In production, Xtream completes cross-cloud VM drills in 7–22 minutes depending on configuration, significantly reducing migration risks.