Regular file server upgrades are indispensable to improve performance, robustness, and power consumption. In upgrading file servers, it is crucial to quickly migrate file-sharing services between heterogeneous servers with little downtime while minimizing performance interference. We present a practical quick file server migration scheme based on the postcopy approach that defers file copy until after switching servers. This scheme can (1) reduce downtime with on-demand file migration, (2) avoid performance interference using background migration, and (3) support heterogeneous servers with stub-based file management. We discuss several practical issues, such as intermittent crawling and traversal strategy, and present the solutions in our scheme. We also address several protocol-specific issues to achieve a smooth migration. This scheme is good enough to be adopted in production systems, as it has been demonstrated for several years in real operational environments. The performance evaluation demonstrates that the downtime is less than 3 seconds, and the first file access after switching servers does not cause a timeout in the default timeout settings; it takes less than 10 seconds in most cases and up to 84.55 seconds even in a large directory tree with a depth of 16 and a width of 1,000. Although the total migration time is approximately 3 times longer than the traditional precopy approach that copies all files in advance, our scheme allows the clients to keep accessing files with acceptable overhead. We also show that appropriate selection of traversal strategy reduces tail latency by 88%, and the overhead after the migration is negligible.

中文翻译：

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实用的快速文件服务器迁移

定期文件服务器升级对于提高性能、稳健性和功耗是必不可少的。在升级文件服务器时，关键是要在异构服务器之间快速迁移文件共享服务，同时减少停机时间，同时最大限度地减少性能干扰。我们提出了一种实用的快速文件服务器迁移方案，该方案基于将文件复制推迟到切换服务器之后的后复制方法。该方案可以（1）通过按需文件迁移减少停机时间，（2）使用后台迁移避免性能干扰，以及（3）支持具有基于存根的文件管理的异构服务器。我们讨论了几个实际问题，例如间歇性爬行和遍历策略，并在我们的方案中提出了解决方案。我们还解决了几个特定于协议的问题，以实现平滑迁移。该方案足以在生产系统中采用，因为它已在实际操作环境中证明了几年。性能评估表明宕机时间小于3秒，在默认超时设置下，切换服务器后第一次文件访问不会导致超时；在大多数情况下，它只需要不到 10 秒，即使在深度为 16、宽度为 1,000 的大型目录树中，也最多需要 84.55 秒。尽管总迁移时间比预先复制所有文件的传统预复制方法长约 3 倍，但我们的方案允许客户端以可接受的开销继续访问文件。We also show that appropriate selection of traversal strategy reduces tail latency by 88%, and the overhead after the migration is negligible.