View source for Parallel Target Migration HLD

= Multithreaded utility for parallel OST migration =


{| class="wikitable"
! Author !! Version !! Date !! Change
|-
| Sergey Noskov || 0.1 || 2026-10-10 || Initial version. Background
|}

== Background ==

Large-scale Lustre installations need to relocate data between OSTs for storage maintenance, hardware replacement, capacity balancing, and OST evacuation. These operations may involve millions of files and run for days while the filesystem continues serving applications.

Lustre provides per-file migration mechanisms, but managing a complete migration campaign requires parallel scheduling, workload control, retries, and reliable tracking of completed and unfinished work. Combining these capabilities in a standalone utility would reduce the need for site-specific scripts and simplify operation.

The utility should allow administrators to adjust concurrency during execution and save progress at safe stopping points for later continuation. It should handle long paths and support both mirrored and erasure-coded layouts, preserving the required data protection and verifying the resulting placement before reporting success.