What is a Disk Quota?

The disk quota is a protocol that is often used by system administrators to ensure that available resources are equitably and reasonably distributed among the users of the operating systems that are used by a home or business network. This process of managing the file system usage of each work station within the network helps to prevent the use of more resources by one user to the detriment of another user in the group. The system administrator normally has the ability to assign disk quotas on both a per work station basis as well as on an individual user basis.

There are essentially two recognized types of disk quota implementation in use today. The first is known as a block or usage quota. With this approach, the system administrator will set limits on the amount of disk space that can be used by any one system user. By setting a usage quota, the administrator can make sure that all users of the network have reasonable access to resources needed to perform essential tasks, but do not use up so many resources that other users are left with diminished reserves.

A second way to manage the function of a disk quota is known as an inode or file quota. Rather than being concerned with the amount of disk space utilized by a given user, this approach to managing the disk quota focuses on limiting the total number of directories or files that can be created. One advantage to this approach is that it can cut down on the creation of multiple files or directories that are so similar in nature and content that they should have been contained in one file or directory in the first place.

Most administrators make use of some type of notification or warning when a user is about to exceed his or her current disk quota. This is often referred to as a soft quota and will make use of a simple notification through the network that the user is nearing his or her limit. However, this approach does not include any follow-up action, other than also notifying the administrator that a given user is nearing their assigned disk quota.

A more aggressive notification, known as a hard quota, takes the process past a simple warning. After notifying the user that he or she is nearing their assigned disk quota, the system will effectively shut the user out once the assigned quota is exceeded. This type of system management will require the administrator to intervene, either by increasing the disk quota allotted to the user, or by working with the user to archive or eliminate unnecessary files and reduce the user’s files back to a level below the quota.