Disk Quota

Disk Quota ( engl. disk, hard disk ' and quota, share ', ' quota ') is called the limit of space on storage media such as hard disks, for a single user or a group of users. The mechanism is an integral part of most versions of Unix, or directly into the kernel, usually directly implemented in conjunction with the shared file system. Since Windows 2000 there are disk quotas on for Microsoft operating systems, there generally these disk quota or quota shortly be mentioned.

Details

The goal is generally to set a technical limit for disk space usage to ensure that all users can utilize the available system resources as intended. In environments where space is rented (such as the Web hosting ) you also want to ensure that users only use as much memory as they pay in addition to these quality considerations.

Quota Types

In general, two storage space borders are distinguished, which are set by the system administrator: the so-called soft quota ( a "soft" warning limit that may be exceeded for a short time ) and the hard disk quota ( a "hard" limit that absolutely can not be exceeded ). Sometimes an additional grace period ( "grace period" ) is set, which determines how long the soft limit may be exceeded (see below).

Apart from the distinction between soft limit and hard limit is usually distinguished between the usage quota or block quota and the quota file or inode quota. During block quotas limit the actual maximum space in file quota the number of files and directories (usually inode ) is limited to a maximum.

While the aforementioned quota types usually refers to a directory and its subdirectories, there is also the option to limit disk space per user; this possibility exists about Novell Netware. The user's storage assets, the User Quota, this does not refer to his home directory, but it will take into account all the data, from which the user is listed as owner, no matter which directory of the tree are the data.

Quota violation

Exceeds a user be soft quota, so he usually gets a message from the system. Often an email is sent, for example. Often the system administrator is notified of the incident and at the same time.

Is there a grace period, the system monitors the space development of the relevant user: If in this time of consumption is not reduced below the soft limit, the system disables the additional memory consumption: The soft limit is enforced until the user again to release enough memory.