Windows Server 2012 R2 Large File Copy Stalls at 99 Percent Over SMB 3 Encryption – Fix & Prevention

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

Large encrypted transfers stall near completion, delaying replication and archival operations.

Environment & Reproduction

Seen on high-throughput links with mixed offload settings under strict encryption policy.

Root Cause Analysis

Encryption overhead and retransmissions combine with feature mismatch to create stalls.

Quick Triage

Validate encryption status, retransmission rates, and NIC offload configuration.

Step-by-Step Diagnosis

Collect SMB and network traces to isolate encryption versus transport causes.

Solution – Primary Fix

Standardize NIC settings, apply stable drivers, and tune encryption policy for hardware.

Solution – Alternative Approaches

Use controlled transfer windows or alternate secure channels for very large files.

Verification & Acceptance Criteria

Encrypted transfers complete reliably with expected throughput.

Rollback Plan

Restore previous NIC profile if new tuning reduces stability.

Prevention & Hardening

Validate encrypted SMB performance after each network stack update.

Related Errors & Cross-Refs

Can occur with multichannel negotiation issues and burst packet loss.

Related tutorial: View the step-by-step tutorial for Windows Server 2012 R2.

View all Windows Server 2012 R2 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Use Microsoft SMB security and performance documentation.