The Quick Migration of File Servers
Keiichi Matsuzawa, Mitsuo Hayasaka, Takahiro Shinagawa · 2018
Upgrading file servers is indispensable for improving the performance, reducing the possibility of failures, and reducing the power consumption. To upgrade file servers, files must be migrated from the old to new servers, which poses three challenges: reducing the downtime during migration, reducing the migration overhead, and supporting the migration between heterogeneous servers. Existing technologies are difficult to achieve all of the three challenges. We propose a quick file migration scheme for heterogeneous servers. To reduce the downtime, we exploit the post-copy approach and introduce on-demand migration that allows file access before completing the migration. To reduce the overhead, we introduce background migration that migrates files as soon as possible without affecting the performance and incurs no overhead after the migration. To support heterogeneity, we introduce stub-based file management that requires no internal states of the old server. We implemented our scheme for Linux and supported the NFS and SMB protocols. The experimental results depict that the downtime was a maximum of 23 s in a 4-level 1000-file directory and the migration time was 70 min in NFS and 204 min in SMB with 242 GiB of data.