A disk quota is a set of rules that restrict disk space and the number of files used by a user or a group. A quota can also restrict the total space and files used in a qtree or the usage of users and groups within a qtree. For example, you could create a user quota that specifies that a particular user can use up to 225MB of disk space in a given qtree in a given volume before a warning is issued (soft limit) and up to 250MB maximum (hard limit).
A request that would cause a user or group to exceed an applicable quota fails with a "disk quota exceeded" error. A request that would cause the number of blocks or files in a qtree to exceed the qtree's limit fails with an "out of disk space" error.
User and group quotas do not apply to the root user or to the Windows Administrator account; however, tree quotas do apply even to root and the Windows Administrator account.
This information is stored in the /etc/quotas file. Data ONTAP reads this file to determine how to apply quotas. All quotas are established on a per-volume basis.