Why does my user quota show over limit or negative available space?

Applicable Products

• All QNAP NAS with QTS

Scenario

On the Control Panel > Quota page, some users may see that Used Size exceeds the quota limit or that Available space is shown as a negative value, even though the user does not appear to store that much data.

Root Cause

This issue is caused by a User ID (UID) mapping problem:

• QTS calculates user quota usage based on file ownership (UID).
• If files or folders are owned by a UID that is mapped to an unexpected or incorrect user account, their size will be counted toward that user’s quota.
• This can result in incorrect quota usage, including over-quota status or negative available space.

Solution

Warning: Deleting or disabling user accounts can affect user access, shared folder permissions, and applications that rely on those accounts. Before proceeding, ensure you understand the impact and back up important data if necessary.

Method 1: Find and fix file ownership using File Station 

Use this method if the number of incorrectly owned files is manageable and you can adjust ownership from the web interface.

1. Log in to QTS as an administrator.
2. Open File Station.
3. Use the advanced search function and fill with the issue user in "Owner" to find files or folders owned by the affected user.
4. If too many results are returned, search one folder at a time instead of the entire NAS.
5. Identify files or folders that should not belong to that user.
6. Change their ownership to the correct user or to an administrator account.

After ownership is corrected, the system will automatically recalculate quota usage.

Method 2: Free the problematic UID and reassign it to an administrator

Use this method if many files are owned by a problematic UID and changing ownership manually is not practical.

1. Delete the user account that currently uses the problematic UID. This action frees up that UID. (Existing files owned by that UID are not deleted.)
2. Create a new administrator account.
3. The system automatically assigns the newly created account the freed UID by default.

• Administrator accounts are not restricted by user quota.
• Existing files owned by that UID will no longer affect regular users’ quota usage.

Method 3: Disable the affected user and create a new account

Use this method if you prefer to keep the existing UID and data as-is, and simply provide the user with a fresh account and quota.

1. Disable the user account that shows incorrect quota usage.
2. Create a new user account for the same person.
3. Assign the required permissions to the new account.

Further Reading

• How could a regular user know the quota left on the NAS?
  
• Time Machine Backup with Quota higher than 2TB