Empty trash-bin when runnig out of physical disk space

[avanc]

Steps to reproduce

1. Create user with quota of 20GB
2. However, provide physical disk space of less than 20GB
3. Copy and remove a lot of data

Expected behaviour

NC should empty trash to free space if physical disk space gets low.

Actual behaviour

NC detects that the user only uses 10 of 20GB. Thus, trash is allowed to be 5GB. While adding new data, the user runs out of disk-space (physical) although some space would be available when removing trash.
This is inconsistent, as the user gets reported, that he is running out of free space at index.php/apps/files in the lower left corner (in my case "7.6GB of 7.8GB is used" although quota is at 20GB).

Server configuration

Operating system:
Arch Linux
Web server:
Apache

Database:
MariaDB

PHP version:
PHP7

Nextcloud version: (see Nextcloud admin page)
14.0.1

Updated from an older Nextcloud/ownCloud or fresh install:
Regular update

Where did you install Nextcloud from:
Arch Linux package manager

Login as admin user into your Nextcloud and access 
http://example.com/index.php/settings/integrity/failed 
paste the results here.

No errors have been found.

Are you using external storage, if yes which one: local/smb/sftp/...
No

Are you using encryption: yes/no
no

Are you using an external user-backend, if yes which one: LDAP/ActiveDirectory/Webdav/...
no

[nextcloud-bot]

GitMate.io thinks possibly related issues are #5534 (Empty trash), #7053 (Emptying trash bin gives the impression of failing, and removes too much), #10862 (Trash-bin ignores trashbin_retention_obligation), #1112 (Errors accessing trash bin), and #1332 (API for the trash-bin).

[skjnldsv]

Like mentioned in the docs https://docs.nextcloud.com/server/stable/user_manual/files/quota.html

Deleted files that are still in the trash bin do not count against quotas. The trash bin is set at 50% of quota. Deleted file aging is set at 30 days. When deleted files exceed 50% of quota then the oldest files are removed until the total is below 50%.

Please configure your trashbin threshold to delete files earlier and adjust the quota accordingly :)