One runaway folder should never fill the whole NAS. Set Synology shared folder quotas on Btrfs, use user quotas as the second lever, and size both honestly.
NAS storage never fills evenly. It fills one folder at a time - camera exports, a video project, someone's "temporary" backup of their entire laptop - while every other team suddenly gets "disk full" errors on a NAS that was half empty in their mind. A quota is how one team's appetite stops becoming everyone's outage.
Example values - one runaway folder can starve every other team on the same volume.
Without a quota, every shared folder on a volume can grow until the volume itself is 100 percent full - at which point all folders fail together, backups choke, and DSM starts complaining in ways that look like hardware faults. A quota converts a crisis into a private, early warning: one folder stops at its limit while the rest of the office keeps working.
DSM also supports a quota per user on each volume (Control Panel → User & Group → select user → Edit → Quota). User quotas cap the total a person can store across folders on that volume - useful against the single heavy uploader. Be careful using both levers at once: when a write fails, you will have to work out which of the two limits said no, and so will your confused user.
A quota is a planning tool, not a punishment. Set it around two to three times the folder's current size for working teams, review the biggest folders monthly in Storage Manager, and raise limits deliberately when a team grows. The one folder that should almost always have a quota is anything automated - surveillance exports, backup targets, sync folders - because machines never notice they are filling a disk.
The full shared folder setup - creating folders, users and permissions - shown live on a Synology NAS.
▶️ Watch Full VideoShared folder quotas require the volume to use the Btrfs file system. On an ext4 volume the option simply does not appear in the folder's Advanced settings. User quotas per volume are available more widely, and are often the practical fallback on older volumes.
New writes to that folder fail - users see errors when saving or copying - while every other folder on the volume keeps working normally. Nothing is deleted automatically; an admin raises the quota or the team clears space.
Yes, if no user quota is set. Home folders live on the same volume as everything else. Set per-user quotas on the volume, and remember that sync tools on a user's PC will happily upload until something stops them - the quota is that something.