Can I reduce the Time Machine backup folder maximum size in HBS3 ?
Last modified date:
2026-08-06
Applicable Products
- QNAP NAS using QTS with HBS3 Time Machine service
Scenario
A user set the Time Machine backup folder maximum size too high in HBS3 (3 TB) and wants to reduce it to 2 TB after cleaning old backups.
The main concern is whether lowering the limit in HBS3 is safe and whether it can cause backup issues.
Solution
Preconditions
- Check current actual Time Machine usage from macOS/NAS and make sure it is at or below the new target limit.
- Confirm your Time Machine target is the HBS3-managed shared-folder path (QTS behavior).
Step-by-Step
- Open HBS3 on the NAS.
- Go to the Time Machine settings page where backup folder and maximum capacity are configured.
- Change the maximum size from the old value (for example, 3 TB) to the new value (for example, 2 TB).
- Save the setting.
- Trigger or wait for the next Time Machine backup cycle from the Mac.
- Verify backup continues normally.
What to Expect After Reducing the Limit
- Lowering the max value does not immediately delete all old backup data by itself.
- Time Machine manages retention/purging over time based on available quota and backup behavior.
- If usage is still above the new limit, backup may pause/fail until enough old snapshots are purged.
Warning
Do not reduce the limit too aggressively. Keep headroom for upcoming incremental backups to avoid frequent quota-pressure events.
Validation Checklist
- New max-size value is visible in HBS3 Time Machine settings.
- Mac can still run Time Machine backup without authentication or destination errors.
- NAS storage usage trend stabilizes and old versions are purged as expected over subsequent cycles.
For further assistance, ask other users and QNAP experts in the community. Go to QNAP Community
