Chapter 9: Disk Quotas

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Even though disk space seems to be a nearly endless subject in that the amount of disk space and the sizes of disks seem to be getting bigger and bigger, the fact is that disk "quotaing" is more important than ever. It is very much a case of build it and they will come — or, rather, put the space there and they will fill it, and quickly. The explosion in disk space has been closely paralleled by the growth of file sizes in recent years. Pay no attention to disk quotas, and in a short time any enterprise will be chock full of MP3s and other miscellany, and users will be screaming for more space. In addition to disk quotas, control of free space must be maintained. You do not want disks to fill up, and you want to be able to inform users ahead of time when they need to start thinking about deletions. Performance, in fact, suffers when disks fill up. So, here are the basics of the subject and some tools to help you stay on top of the disk space situation.

What Is a Disk Quota?

Disk quotas have been with us for quite some time. In mainframe and other legacy environments, for instance, they are a firmly established tool for staying in command of available space. Essentially, a quota is an assigned limit or amount for something. When it comes to disk space, the quota indicates the maximum amount of space assigned to a user or a directory. Disk quotas, then, control space consumption and prevent one greedy individual, for example, from consuming everyone else's space and causing system crashes and other situations.

Microsoft released Windows NT without any kind of disk quotaing features. It was left up to software vendors to develop the necessary disk quota management utilities to do the job. Even with the release of a built-in quota utility in Windows 2000, though, third-party quota products are still recommended as they have much more functionality and have greater flexibility than the scaled-down tool inside the operating system.

Basically, disk quota tools work by monitoring partitions/volumes, directories, files, and user space. They are used to set limits and warning thresholds for space and directory consumption. If users meet or exceed their space thresholds, various management actions can occur, including alerting users (and their administrators) that they have run out of free space or that they have exceeded, say, 70% usage of a disk quota. Users receive e-mails or on-screen notifications about quota-related matters. Administrators can view the event log as well as disk space reports and can alter the various quota thresholds.

Some tools allow the user to save the current document, whereas others leave users high and dry; as soon as a space quota is exceeded, the user is allotted no more space, thus losing the open document. Further, it is important to be aware that some disk quota tools merely alert users to the fact that the quota has been exceeded and can do nothing to restrict further disk usage.

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