Quotas

Quotas Overview:

Quotas provide a way to restrict or track the disk space and number of files used by a user, group, or qtree

Why you use quotas:
You can use quotas to limit resource usage, to provide notification when resource usage reaches specific levels, or to track resource usage.

You specify a quota for the following reasons:
To limit the amount of disk space or the number of files that can be used by a user or group, or that can be contained by a qtree.
To track the amount of disk space or the number of files used by a user, group, or qtree, without imposing a limit.
To warn users when their disk usage or file usage is high.
 
Overview of the quota process:
Quotas can be soft or hard. Soft quotas cause Data ONTAP to send a notification when specified thresholds are exceeded, and hard quotas prevent a write operation from succeeding when specified thresholds are exceeded.

When Data ONTAP receives a request to write to a volume, it checks to see whether quotas are activated for that volume. If so, Data ONTAP determines whether any quota for that volume (and, if the write is to a qtree, for that qtree) would be exceeded by performing the write operation. If any hard quota is exceeded, the write operation fails, and a quota notification is sent. If any soft quota is exceeded, the write operation succeeds, and a quota notification is sent.
 

Special kinds of quotas:

Default -- You can use default quotas to apply a quota to all instances of a given quota type. For example, a default user quota affects all users on the system for the specified volume or qtree. . In addition, default quotas enable you to modify your quotas easily.
Explicit --- You can use explicit quotas to specify a quota for a specific quota target or to override a default quota for a specific target.
Derived -- 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.
Tracking -- Tracking quotas generate reports of the disk and file usage and do not limit resource usage. When tracking quotas are used, modifying quota values is less disruptive, because you can resize quotas rather than turning them off and back on.
 

Differences among hard, soft, and threshold quotas:

Hard quotas prevent operations while soft quotas trigger notifications.
Hard quotas impose a hard limit on system resources; any operation that would result in exceeding the limit fails.
The following attributes show hard quotas:

 

• Disk field
• Files field
  
  Soft quotas send a warning message when resource usage reaches a certain level, but do not affect data access operations, so you can take appropriate action before the quota is exceeded. 

The following attributes show soft quotas:

• Threshold field
• Soft Disk field
• Soft Files field

How quotas are activated:

You can activate quotas at the volume level. 
New quotas and changes to quotas do not take effect until they are activated. 
Quotas are activated either by initializing (turning them on) or by resizing. Turning off quotas and turning them on again is called reinitializing. 
The initialization process involves two parts: quota on & quota resize 
 
The length of the activation process and its impact on quota enforcement depends on the type of activation:

The initialization process involves two parts: a quota on command and a quota scan of the volume's entire file system. The scan begins after the quota on command completes successfully. The quota scan can take some time; the more files that the volume has, the longer it takes. Until the scan is finished, quota activation is not complete and quotas are not enforced.
The resize process involves only a quota resize command. Because it does not involve a quota scan, resizing takes less time than a quota initialization. During a resize process, quotas are enforced.
By default, the quota on and quota resize commands run in the background, which permits you to use other commands at the same time.
 

When to resize or reinitialize:

Quota resizing is faster than quota initialization, you should use resizing whenever possible. However, resizing only works for certain types of quota changes. 
Full quota reinitialization is required if you make certain small or extensive changes to your quotas. 

You can resize quotas when making the following types of changes to the quotas file:
Changing an existing quota.
For example, changing the limits of an existing quota.

Adding a quota for a quota target for which a default quota or a default tracking quota exists.
Deleting a quota for which a default quota or default tracking quota entry is specified.
Combining separate user quotas into one multi-user quota.
Example of quotas changes that require initialization
Suppose you have a volume that contains three qtrees and the only quotas in the volume are three tree quotas. You decide to make the following changes:

Add a new qtree and create a new tree quota for it.
Add a default user quota for the volume.
Both of these changes require a full quota initialization. Resizing does not make the quotas effective.
 

Quota reports:

Quota reports enable you to see what quotas Data ONTAP is applying. You can change the format of the quota report and how user IDs are displayed using the options for the quota report command.

Volume quota report

Volume quota report displays the quota report for volumes - This command is available to cluster and Vserver administrators at the admin privilege level. 

This command displays the quota report for all volumes in each Vserver that are online and for which quotas are activated. Quota report includes the quota rules (default, explicit, and derived) in effect and the associated resource usage (disk space and files). If quotas are still initializing for a specific volume, that volume is not included. This command is not supported on Infinite Volumes. 

A quota report is a resource-intensive operation. If you run it on many volumes in the cluster, it might take a long time to complete. A more efficient way would be to view the quota report for a particular volume in a Vserver. 
 
Note: Quotas does not affect/work for Administrators
 
 

 

Known Errors:

The specific failure symptom can vary depending on your configuration and version of Data ONTAP.