Dell Unity supports file system user quotas, quota trees, and quota tree user quotas. All three types of quotas can coexist on the same file system and may be used in conjunction to achieve finer grained control over storage usage.
File system user quotas are set at a file system level and limit the amount of space a particular user may use from a file system. Administrators can also choose whether to enforce user quotas for the file system. If quotas are not enforced, they will still be tracked for the file system, but users will not have their file system usage restricted in accordance with the quotas. By default, quotas are not enforced, however this can be changed in the Manage Quota Settings dialog box along with the default user quotas. Default file system level quota limits are applied automatically to all users who access a file system. However, these can be overridden for specific users as necessary by creating a new user quota in Unisphere. Because all unspecified users are subject to the default quota settings by default, there is no ability to “delete” user quotas. Instead a user quota can be set to 0 to allow unlimited access, or reset to the default limits, in which case the particular entry would be removed from the user quota list in Unisphere but remain in effect with the default settings.
Quota trees limit the maximum size of a particular directory in a file system. Unlike user quotas, which are applied and tracked on a user by user basis, quota trees are applied to directories within the file system. On Dell Unity, quota trees can be applied on new or existing directories.
If an administrator specifies a nonexistent directory when configuring a new quota tree, the directory will be automatically created as part of quota configuration. However, an administrator may also specify an existing file system directory with existing data when creating a quota tree, allowing the ability to implement quotas on existing file system and directory structures after they have already been in production. If a tree quota is deleted, the directory itself remains intact and all files continue to be available.
Quota trees may not be nested within a single directory. For example, if a quota tree is created on /directory1, another quota tree cannot be created on /directory1/subdirectory1. However, it is possible to have quota trees on /directory2, /directory3, and so on. Once a quota tree has been created, it is also possible to create additional user quotas within that specific directory. Like file system level user quotas, the administrator has the option to whether to enforce user quotas specific to this directory and set the default quota limits for the directory. As an example, user Chuck may have a user quota of 25 GB at the file system level, and then the additional restriction of a 10 GB user quota within /directory1 which is limited to 100 GB for all users combined. The figure below shows an example of the quota hierarchy possible with the combination of user quotas and quota trees, including directory-specific user quotas.