SPMT Needs True Mirror Mode and Resource Throttling

Subject: SPMT Needs True Mirror Mode and Resource Throttling

SPMT incremental migration does not behave like a true synchronization or mirror operation. New and modified files are copied, but deleted, renamed, or moved files are not reconciled at the destination, often resulting in orphaned content and duplicates. Microsoft has previously confirmed this as expected behavior. 

Administrators have had reliable mirror-style functionality available since the circa 1990s through tools such as Robocopy. In comparison, SPMT's incremental migration capability feels incomplete for modern enterprise migration scenarios.

Requested enhancements:

• Optional mirror mode similar to robocopy /MIR
• Delete destination content that no longer exists in the source
• Detect and process renames
• Detect and process moves
• Pre-migration analysis and dry-run reporting
• Configurable safeguards for deletions

Additionally, SPMT appears to consume storage resources aggressively. During migrations, disk I/O activity can become saturated and disk idle time can fall close to zero regardless of migration batch size. This behavior can negatively impact file servers and production workloads.

Requested performance controls:

• I/O throttling
• CPU throttling
• Concurrency controls
• Bandwidth limits
• Scheduling and business-hours policies
• Dynamic backoff based on source-server load

Current behavior requires administrators to perform manual cleanup and reconciliation after incremental migrations while also managing significant infrastructure impact during migration runs. A modern migration tool should provide both synchronization intelligence and resource governance controls.

Frankly, from an infrastructure perspective, your complaint about the I/O behavior is probably the stronger one. Many migration tools deliberately maximize throughput, but not providing an obvious way to cap I/O, threads, or overall system impact can be problematic in production environments. The lack of mirror semantics combined with aggressive scanning/copy behavior is what tends to frustrate admins the most.