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A disk quota is a limit set by a system administrator that restricts certain aspects of file system usage on modern operating systems. The function of using disk quotas is to allocate limited disk space in a reasonable way.[1]
There are two basic types of disk quotas. The first, known as a usage quota or block quota, limits the amount of disk space that can be used. The second, known as a file quota or inode quota, limits the number of files and directories that can be created.
In addition, administrators usually define a warning level, or soft quota, at which users are informed they are nearing their limit, that is less than the effective limit, or hard quota. There may also be a small grace interval, which allows users to temporarily violate their quotas by certain amounts if necessary.
Quotasedit
Disk quotas are typically implemented on a per-user or per-group basis. That is, a system administrator defines a usage or file quota specific to a certain user or group. In some filesystems (e.g. ext4, XFS, f2fs, ZFS, Lustre) it is also possible to also define block and inode quota limits for a particular project or directory, by adding a project ID to files that directory tree and defining quota limits for the project ID.
In doing so, an administrator can prevent one user from consuming an entire file system's resources, or create a system of tiered access, whereby users can have different levels of restriction. This is used, for example, by web hosting companies to provide different levels of service based upon the needs and means of individual clients.
In most cases, quotas are also specific to individual file systems. Should an administrator want to limit the usage of a specific user on all file systems, a separate quota would have to be specified on each.
When a soft quota is violated, the system normally sends the user (and sometimes the administrator as well) some sort of message. No further action is typically taken.
Some systems prevent disk write operations that would result in hard quota violations from completing successfully, while others wait until the quota has been physically violated before denying write requests. The user is typically notified through the failed write operation error messages generated by the violating applications, while the administrator is almost always sent a notification as well.
Disk quotas are supported by most modern operating systems, including Unix-like systems, such as AIX (using JFS or JFS2 filesystem), Linux (using ext3, ext4, ext2, XFS (integrated support) among other filesystems), Solaris (using UFS or ZFS), Microsoft Windows starting with Windows 2000, Novell NetWare, VMS, and others. The method of administration for disk quotas varies between each of these operating systems. Unix-like systems typically provide a quota command for both administration and monitoring; graphical front-ends to the command may also be used. Unix and Unix-like operating systems frequently feature a grace period where users may exceed their quota limits for a brief period of time. Windows 2000 and newer versions use the "Quota" tab of the disk properties dialog. Other systems provide their own quota management utilities.
Common Unix disk quota utilitiesedit
quota - display a user's file system disk quota and usage;
edquota - Edit user quotas for file system;
setquota - Set disk quotas for file system;
repquota - Summarize quotas for a file system;
quotacheck - File system quota consistency checker;
^Posodobitev, Zadnja (24 March 2023). "Disk quota system concept". IBM.com. Retrieved 8 April 2024.{{cite web}}: CS1 maint: url-status (link)
April 11, 2024
disk, quota, this, article, multiple, issues, please, help, improve, discuss, these, issues, talk, page, learn, when, remove, these, template, messages, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, ci. This article has multiple issues Please help improve it or discuss these issues on the talk page Learn how and when to remove these template messages This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Disk quota news newspapers books scholar JSTOR April 2024 Learn how and when to remove this template message This article s lead section may be too short to adequately summarize the key points Please consider expanding the lead to provide an accessible overview of all important aspects of the article January 2015 Learn how and when to remove this template message A disk quota is a limit set by a system administrator that restricts certain aspects of file system usage on modern operating systems The function of using disk quotas is to allocate limited disk space in a reasonable way 1 Contents 1 Types of quotas 2 Quotas 3 Common Unix disk quota utilities 4 See also 5 External links 6 ReferencesTypes of quotas editThere are two basic types of disk quotas The first known as a usage quota or block quota limits the amount of disk space that can be used The second known as a file quota or inode quota limits the number of files and directories that can be created In addition administrators usually define a warning level or soft quota at which users are informed they are nearing their limit that is less than the effective limit or hard quota There may also be a small grace interval which allows users to temporarily violate their quotas by certain amounts if necessary Quotas editDisk quotas are typically implemented on a per user or per group basis That is a system administrator defines a usage or file quota specific to a certain user or group In some filesystems e g ext4 XFS f2fs ZFS Lustre it is also possible to also define block and inode quota limits for a particular project or directory by adding a project ID to files that directory tree and defining quota limits for the project ID In doing so an administrator can prevent one user from consuming an entire file system s resources or create a system of tiered access whereby users can have different levels of restriction This is used for example by web hosting companies to provide different levels of service based upon the needs and means of individual clients In most cases quotas are also specific to individual file systems Should an administrator want to limit the usage of a specific user on all file systems a separate quota would have to be specified on each When a soft quota is violated the system normally sends the user and sometimes the administrator as well some sort of message No further action is typically taken Some systems prevent disk write operations that would result in hard quota violations from completing successfully while others wait until the quota has been physically violated before denying write requests The user is typically notified through the failed write operation error messages generated by the violating applications while the administrator is almost always sent a notification as well Disk quotas are supported by most modern operating systems including Unix like systems such as AIX using JFS or JFS2 filesystem Linux using ext3 ext4 ext2 XFS integrated support among other filesystems Solaris using UFS or ZFS Microsoft Windows starting with Windows 2000 Novell NetWare VMS and others The method of administration for disk quotas varies between each of these operating systems Unix like systems typically provide a quota command for both administration and monitoring graphical front ends to the command may also be used Unix and Unix like operating systems frequently feature a grace period where users may exceed their quota limits for a brief period of time Windows 2000 and newer versions use the Quota tab of the disk properties dialog Other systems provide their own quota management utilities Common Unix disk quota utilities editquota display a user s file system disk quota and usage edquota Edit user quotas for file system setquota Set disk quotas for file system repquota Summarize quotas for a file system quotacheck File system quota consistency checker quotaon Turn file system quotas on and off etc fstab Linux or etc vfstab Solaris list of default parameters for each file system including quota status See also editFile systemExternal links editAIX disk quota system overview IBM Solaris disk quota tutorial Linux DiskQuota homepageReferences edit Posodobitev Zadnja 24 March 2023 Disk quota system concept IBM com Retrieved 8 April 2024 a href Template Cite web html title Template Cite web cite web a CS1 maint url status link Retrieved from https en wikipedia org w index php title Disk quota amp oldid 1218226864, wikipedia, wiki, book, books, library,
