Dell PowerFlex Appliance with PowerFlex 4.x Administration Guide

User quotas

User quotas are set at a file system level and limit the amount of space a user may consume on a file system. Quotas are disabled by default, but this can be enabled in the quota properties page dialog box along with the default user quota settings. The default quota limits are applied automatically to all users who access the file system. However, the default limits can be overridden for specific users by creating a new user quota entry in PowerFlex Manager.

Because all unspecified users are subject to the default quota settings, there is no ability to delete a user quota. Instead, a user quota can be set to 0 to allow unlimited access. Alternatively, a user quota can be set to inherit the default limits.

Tree quotas

Quota trees limit the maximum size of a directory on 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. 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 is 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.

In PowerFlex file, the quota grace period setting only applies to user quotas since each tree quota can have its own individual grace period setting. Newly created tree quotas have a default grace period setting of 7 days, and this can be customized during creation or afterwards.

User quotas on tree quotas

Once a quota tree is created, it is also possible to create additional user quotas within that specific directory by choosing to enforce user quotas. When multiple limits apply, users are bound by the limit that they reach first. As an example, a single user may be bound by the following limits on a file system:

• File system user quota: 25 GB
  • This user has a limit of 25 GB across the entire file system
• Tree quota (/directory1): 100 GB
  • Data from all users in this directory may not exceed 100 GB
• User quota on tree quota (/directory1): 10 GB
  • This user cannot consume more than 10 GB on this directory

Quota limits

All quotas consist of three major parameters which determine the amount of space that can be consumed on a file system and define the behavior when a limit is being approached or exceeded. These parameters are:

• Soft limit (GB)
• Grace period (time)
• Hard limit (GB)

The soft limit is a capacity threshold which triggers the grace period timer to start. For as long as the soft limit is exceeded, the grace period continues to count down. If the soft limit remains exceeded long enough for the grace period to expire, no new data may be added by the user or to the directory. The grace period has a minimum value of 1 minute and maximum value of unlimited. However, if enough data is removed from the file system or directory to reduce the utilization below the soft limit before the grace period expires, data can continue to be written normally. Administrators can also allow users to continue writing data by increasing the value of the soft limit.

A hard limit is also set for each quota configured. Upon reaching a hard limit, no new data can be added to by the user or to the directory. When this happens, the quota must be increased, or data must be removed from the file system before additional data can be written.