Fixes for quirky disk quotas

Disk quotas can help administrators manage a server's disk storage resources. However, disk quotas can be quirky; applying a quota doesn't always have the anticipated effect. Here's what to do when things go wrong.

Disk quotas can go a long way toward helping administrators manage a server's disk storage resources.

Most file servers are equipped with huge hard disks or disk arrays. Still, these servers have a finite storage capacity that must be shared by many users, while some of it is reserved for the organization's future needs.

Disk quotas ensure that server disk resources are divided equitably and that the server will not run out of disk space due to a careless user. However, disk quotas can be quirky; applying a quota doesn't always have the anticipated effect. Before discussing why this is, let's go over the process for creating disk quotas.

Disk quotas are managed on a per-volume basis. To set a quota on a volume:

  1. Open My Computer.
  2. Right-click on the volume you want to impose a quota on.
  3. Select the Properties command from the resulting shortcut menu. Windows will now display the volume's properties sheet.
  4. Select the properties sheet's Quota tab, then select the Enable Quota Management check box, as shown on the screen-shot below.

Setting disk quotas with the Quota tab

The Quota tab allows you to set a default quota for the volume that applies to any new users created. You'll be able to set a disk space limit and a warning level. If you wanted to limit users to using 100 MB of disk space, you could set the warning level to 80 MB, so the users will know when they're getting close to their limit.


Note: At the bottom of the screen shot there's a check box you can use to deny disk space to users who have exceeded their quota. Use it with caution; it can prevent users from being able to save their work if they're too close to their limit. Disk quotas: Not too high, not too low

I once did a consulting project for a company that had implemented quotas on user workstations rather than just on servers. There's usually no reason to put quotas on workstation hard drives, because users should be saving data to network servers, not to local hard drives. But this company did it anyway. Windows writes files to the C: drive as part of the boot and logon processes. Whoever had implemented the quotas had set them too low, so some users were unable to log into their workstations as a result.

The Quota tab is simple. But some beginning administrators miss the fact that these quotas apply only to new users. You have to establish separate quotas for existing users, which you can do by clicking the Quota Entries button.

Windows will now display a list of the existing quota entries. To add a new quota entry, click the New Quota Entry icon. You'll be prompted to enter the name of the user you want to apply the quotas to. Unfortunately, you cannot apply quotas to a group, but you can select multiple users simultaneously. After selecting a user, you'll see a screen that has the same basic options as the screen shown above. You'll then use this screen to set the quotas for the individual user.

When things go wrong: Troubleshooting quotas

As simple as it is to set up a disk quota, things can go wrong. The most common problems involve users being given a different amount of disk space than what was mandated by the quota. When discrepancies occur, the user is usually given less disk space than what the quota specifies.

Actually, the only time that Windows gives a user less disk space than what their quota allows is when the server runs out of disk space. However, there are other circumstances that can create the illusion of a user receiving less disk space than what is granted to them by the quota.

The reason for this is that users typically think of quotas in terms of space occupied by files they have stored on the volume. Technically, however, a quota takes into consideration any file that a user owns. For example, if a user created a file and then gave it to another user, the user might still be the file's owner (depending on the individual circumstances), and the file would therefore be counted against the user's quota.

Also, many users don't consider the recycle bin. Files in the recycle bin count against the user's quota. (Since the recycle bin exists on the workstation's hard drive, this would only hold true if quotas were implemented on the local workstations.)

Compressed files can also lead to confusion. When determining how much disk space a user has consumed, Windows looks at the original size of a compressed file, not at the actual amount of space the file is consuming on the hard disk in its compressed form.

Some situations can cause a user to receive more disk space than what their quota allows. Disk quotas are based on file ownership. Typically, a file's owner is the user who created the file (unless someone else takes ownership later on). The problem with this is that Windows Server 2003 supports the use of three file systems: FAT, FAT-32 and NTFS. Of these, NTFS is the only one that acknowledges the concept of file ownership (or of quotas for that matter).

Now, imagine that a server contains a FAT-32 partition filled with user data. The volume of data is starting to get out of hand, so the admin decides to implement disk quotas. But before disk quotas can be employed, the file system must be converted to NTFS. Since FAT-32 does not record a file's owner, Windows sets each file's owner attribute to Administrator during the file system conversion process. This means that none of the files that existed prior to the conversion will count toward users' disk quotas unless the ownership information is reset.

About the author:
Brien M. Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Windows 2000 Server, Exchange Server and IIS. He has served as CIO for a nationwide chain of hospitals and was once in charge of IT security for Fort Knox. He writes regularly for SearchWinComputing.com and other TechTarget sites.

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This was first published in March 2007

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