Книга: Windows Server 2012 R2 Storage, Security, & Networking Pocket Consultant

Understanding NTFS disk quotas and how NTFS quotas are used

Understanding NTFS disk quotas and how NTFS quotas are used

Administrators use NTFS disk quotas to manage disk space usage for critical volumes, such as those that provide corporate data shares or user data shares. When you enable NTFS disk quotas, you can configure two values:

? Disk quota limit Sets the upper boundary for space usage, which you can use to prevent users from writing additional information to a volume, to log events regarding the user exceeding the limit, or both.

? Disk quota warning Warns users and logs warning events when users are

getting close to their disk quota limit.

TIP You can set disk quotas but not enforce them, and you might be wondering why you’d want to do this. Sometimes you want to track disk space usage on a per-user basis and know when users have exceeded some predefined limit, but instead of denying them additional disk space, you log an event in the application log to track the overage. You can then send out warning messages or figure out other ways to reduce the space usage.

NTFS disk quotas apply only to end users and not to administrators. Administrators can’t be denied disk space even if they exceed enforced disk quota limits.

In a typical environment, you restrict disk space usage in megabytes (MB) or gigabytes (GB). For example, on a corporate data share used by multiple users in a department, you might want to limit disk space usage from 20 to 100 GB. For a user data share, you might want to set the level much lower, such as from 5 to 20 GB, which restricts the user from creating large amounts of personal data. Often you’ll set the disk quota warning as a percentage of the disk quota limit. For example, you might set the warning from 90 to 95 percent of the disk quota limit.

Because NTFS disk quotas are tracked on a per-volume, per-user basis, disk space used by one user doesn’t affect the disk quotas for other users. Thus, if one user exceeds his limit, any restrictions applied to this user don’t apply to other users. For example, if a user exceeds a 5-GB disk quota limit and the volume is configured to prevent writing over the limit, the user can no longer write data to the volume. Users can, however, remove files and folders from the volume to free up disk space. They can also move files and folders to a compressed area on the volume, which might free up space, or they can elect to compress the files themselves. Moving files to a different location on the volume doesn’t affect the quota restriction. The amount of file space is the same unless the user moves uncompressed files and folders to a folder with compression. In any case, the restriction on a single user doesn’t affect other users’ ability to write to the volume (as long as there’s free space on the volume).

You can enable NTFS disk quotas on the following:

? Local volumes To manage disk quotas on local volumes, you work with the local disk itself. When you enable disk quotas on a local volume, the Windows system files are included in the volume usage for the user who installed those files. Sometimes this might cause the user to go over the disk quota limit so to prevent this, you might want to set a higher limit on a local workstation volume.

? Remote volumes To manage disk quotas on remote volumes, you must share the root directory for the volume, and then set the disk quota on the volume. Remember, you set quotas on a per-volume basis, so if a remote file server has separate volumes for different types of data-that is, a corporate data volume and a user data volume-these volumes have different quotas.

Only members of the Domain Admins group or the local system Administrators group can configure disk quotas. The first step in using quotas is to enable quotas in Group Policy, which you can do at two levels:

? Local Through local Group Policy, you can enable disk quotas for an individual computer.

? Enterprise Through Group Policy that applies to a site, a domain, or an organizational unit, you can enable disk quotas for groups of users and computers.

Having to keep track of disk quotas does cause some overhead on computers. This overhead is a function of the number of disk quotas being enforced, the total size of the volumes and their data, and the number of users to which the disk quotas apply.

Although on the surface disk quotas are tracked per user, behind the scenes Windows Server 2012 R2 manages disk quotas according to security identifiers (SIDs). Because SIDs are tracked by disk quotas, you can safely modify user names without affecting the disk quota configuration. Tracking by SIDs does cause some additional overhead when viewing disk quota statistics for users because Windows Server 2012 R2 must correlate SIDs to user account names so that the account names can be displayed in dialog boxes. This means contacting the local user manager and the Active Directory domain controller as necessary.

After Windows Server 2012 R2 looks up names, it caches them to a local file so that they can be available immediately the next time they’re needed. The query cache is infrequently updated-if you notice a discrepancy between what’s displayed and what’s configured, you need to refresh the information. Usually, this means choosing Refresh from the View menu or pressing F5 in the current window.

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