How derived quotas work

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A quota enforced as a result of a default quota, rather than an explicit quota (a quota with a specific target), is referred to as a derived quota.

The number and location of the derived quotas depends on the quota type:

  • A default tree quota on a volume creates derived tree quotas for every qtree on the volume.

  • A default user or group quota creates a derived user or group quota for every user or group that owns a file at the same level (volume or qtree).

  • A default user or group quota on a volume creates a default user or group quota on every qtree that also has a tree quota.

The settings—​including limits and user mapping—​of derived quotas are the same as the settings of the corresponding default quotas. For example, a default tree quota with a 20-GB disk limit on a volume creates derived tree quotas with 20-GB disk limits on the qtrees in the volume. If a default quota is a tracking quota (with no limits), the derived quotas are also tracking quotas.

To see derived quotas, you can generate a quota report. In the report, a derived user or group quota is indicated by a Quota Specifier that is either blank or an asterisk (*). A derived tree quota, however, has a Quota Specifier; to identify a derived tree quota, you must look for a default tree quota on the volume with the same limits.

Explicit quotas interact with derived quotas in the following ways:

  • Derived quotas are not created if an explicit quota already exists for the same target.

  • If a derived quota exists when you create an explicit quota for a target, you can activate the explicit quota by resizing rather than having to perform a full quota initialization.