Symptoms
Large file transfers hang at completion though small copies succeed.
Use the following observations to establish that this is the specific failure described here, rather than an unrelated outage or different account:
- Failing behavior: Large file transfers hang at completion though small copies succeed.
- Comparison to run: Compare one large file with one small file and inspect destination free space.
- Pass condition: Large test file copies with matching checksum and closes normally.
Why It Happens
Shares, backup jobs and replication paths each have their own permissions, destination rules and histories; a successful connection is not proof of complete content.
Treat these as competing hypotheses, not confirmed diagnoses. Their implications are different:
- SMB durable-handle issue — investigate this first only if the local state or controlled comparison supports it.
- NAS quota exhausted — a second layer that may survive a simple restart and requires a targeted check.
- Client filesystem metadata write stalls — investigate when the first two paths do not account for the observed behavior.
Before Making Changes
Never overwrite sole originals until copy verification succeeds. NAS interfaces may report job-level success while individual file operations, permissions, path mapping or remote copies still differ. Verify at the file level and distinguish the original from a restored copy. Write down the working configuration and, if available, export settings or create a test-only copy before changing account permissions, routes or file locations.
Make one change at a time, note the original value, and repeat the exact same test after each change. If the new outcome is worse, restore that single setting; a full reset would erase evidence and can create additional problems.
Problem-Specific Diagnosis
Begin with this controlled observation: Compare one large file with one small file and inspect destination free space. Record the result and time; a vague report such as “sometimes fails” cannot distinguish the three hypotheses.
| Check | What to do | What the result tells you |
|---|---|---|
| Compare a working path | Compare one large file with one small file and inspect destination free space. | If one controlled route works, the failed route is probably specific to a setting, permission, device, or service rather than a total outage. |
| Check the local state | Check destination volume quotas and available space. | This can expose or rule out smb durable-handle issue without changing several settings together. |
| Inspect the deeper layer | Inspect SMB session logs and NAS disk health during final metadata commit. | Use the evidence to separate nas quota exhausted from client filesystem metadata write stalls; do not assume either is proven. |
If the local comparison is inconclusive, keep the current system unchanged while checking whether nas quota exhausted is consistent with the evidence. If not, investigate client filesystem metadata write stalls rather than applying every possible fix.
Use Beginner for reversible checks; use Advanced only when the comparison indicates a deeper fault. Large file transfers hang at completion though small copies succeed. Run a harmless test and write down the time, device/account, current status indicators and the exact difference from normal behavior. Compare one large file with one small file and inspect destination free space. Do not erase logs or reset the device yet. Check destination volume quotas and available space. Confirm the relevant account, cable, selected output, permission or status before saving changes. If it is already correct, leave it alone and proceed; do not force a change just to try something. Reconnect to share after verifying incomplete file state. Change only this one condition after recording the old value. If it does not improve the result, restore the former value rather than layering additional guesses on top. Large test file copies with matching checksum and closes normally. Repeat the same comparison used in step one. Record what improved, what remains unchanged and whether a reconnect or normal app restart changes the result. Stop here if the expected outcome is stable. Consider smb durable-handle issue, nas quota exhausted and client filesystem metadata write stalls separately. Compare evidence from the working and failing paths, and avoid interpreting a green status indicator as end-to-end proof. Compare one large file with one small file and inspect destination free space. Inspect SMB session logs and NAS disk health during final metadata commit. Focus on logs, state, permissions, protocol negotiation or version support relevant to this failure. Do not collect or share credentials, account tokens or unrelated private content. Try an approved alternate SMB version after recording existing settings. Use an isolated or test-only configuration where possible. Keep an explicit rollback path; do not weaken security, replace backup originals or bypass equipment protection to make one test pass. Large test file copies with matching checksum and closes normally. Observe the behavior through the original trigger again. If the change does not produce this measurable result, undo that change and escalate with the recorded facts, rather than repeating disruptive reset attempts.Step-by-Step Troubleshooting
Capture the failing state
Check the first reversible condition
Apply the lowest-risk targeted fix
Retest and document
Distinguish the competing root causes
Inspect the deeper system layer
Run a second independent isolation test
Validate stability and rollback readiness
Solution Checklist
Common Mistakes to Avoid
- Treating smb durable-handle issue as certain before running the comparison: Compare one large file with one small file and inspect destination free space.
- Trying several changes at once, such as modifying nas quota exhausted and client filesystem metadata write stalls simultaneously, which makes the successful change impossible to identify.
- Ignoring the safety boundary: Never overwrite sole originals until copy verification succeeds.
- Assuming that a status label or progress indicator guarantees the actual action completed; verify the outcome independently.
How to Verify the Fix
Large test file copies with matching checksum and closes normally.
- Repeat the original failing action under equivalent conditions: Large file transfers hang at completion though small copies succeed.
- Run the control again: Compare one large file with one small file and inspect destination free space.
- Check the positive pass condition: Large test file copies with matching checksum and closes normally.
- Recheck after a normal restart, reconnection or scheduled cycle only when it is safe and relevant.
A single passing attempt is useful but may conceal intermittent failures. Record whether the fix survives the triggering condition without requiring a daily workaround.
If the Problem Continues
Use the deeper comparison rather than repeating the first steps: Inspect SMB session logs and NAS disk health during final metadata commit. Try an approved alternate SMB version after recording existing settings.
Collect job ID, anonymized path, protocol, client version and relevant error excerpts without uploading private file contents or exposing NAS management to the public internet.
If the issue affects money, alarms, shared business records, or protective power equipment, stop risky experiments and use the official administrator, provider or manufacturer channel.
Prevent Recurrence
- Keep a record of the previously failing condition: Compare one large file with one small file and inspect destination free space.
- Preserve the corrected behavior: Large test file copies with matching checksum and closes normally.
- Keep tested offline or immutable copies of critical data, record job exclusions, and periodically restore a small sample into a separate test location.
- Review configuration or hardware changes that could reintroduce smb durable-handle issue.
Frequently Asked Questions
Does this symptom prove smb durable-handle issue?
No. Start with the controlled comparison: Compare one large file with one small file and inspect destination free space. Only treat smb durable-handle issue as a candidate until the evidence supports it.
What if the first two checks do not change anything?
Move to a different layer rather than repeating the same action: Inspect SMB session logs and NAS disk health during final metadata commit. That helps determine whether nas quota exhausted or client filesystem metadata write stalls fits the symptoms.
How do I know the repair actually worked?
Use this outcome, not just an on-screen status message: Large test file copies with matching checksum and closes normally. Keep a record of the working state for future troubleshooting.