Quota-Management Solutions

Tools to help you control disk space

A perennial complaint about Windows NT is that the OS lacks quota-management tools. Without quota management, controlling how much disk space your network users fill is difficult. Several storage management companies have developed NT quota-management tools, and these third-party tools won't disappear when Windows 2000 (Win2K) ships. Third-party NT quota-management tools have more power than Win2K Server's fairly rudimentary tools.

Quota Management Fundamentals
The quota-management process is straightforward. The quota manager monitors writes to the disk on protected volumes (i.e., shares, files, folders) according to criteria that the network administrator sets. If the protected volume reaches or exceeds a certain data level, then the quota manager either sends a message to the person writing to the volume that warns that the volume is near quota, prevents the user from writing to the volume altogether, or does both. The mechanics of this process vary from product to product, but the effect is the same: Users can't write to volumes that reach or exceed their preset quota. Quota-management products base quotas on clusters, not on space filled with useful data; therefore, using NTFS on managed volumes is advantageous, because FAT volumes have larger cluster sizes.

Quota Manager and QuotaAdvisor: Similarities, but a Low-Level Difference
NTP Software's Quota Manager 4.03, Enterprise Edition and W. Quinn's QuotaAdvisor 4.0, Enterprise Edition accomplish the same purpose. The biggest difference between the two products is in the way they integrate with the OS. Quota Manager runs as a service and doesn't modify NT, whereas QuotaAdvisor is a filter device driver that intercepts selected calls to the file system driver. Quota Manager changes the permissions on a volume to read-only to keep users from writing to an over-quota volume. QuotaAdvisor uses an I/O filter driver to monitor disk I/O and prevent writes to over-quota volumes. Another difference between the products is in where each stores its quotas: Quota Manager's database of quota objects is in the Registry; QuotaAdvisor stores object and policy information in the root of each volume the product protects.

Modern quota-management tools include some management modules. Both Quota Manager and QuotaAdvisor support integration with email, so quota-related messages can relay through email, rather than through the Messenger service. Currently, QuotaAdvisor supports SNMP; Quota Manager will support SNMP in a future release.

Quota Manager 4.03, Enterprise Edition
Quota Manager is a service-based management system that operates by monitoring volume size and write activity. Whenever you access a managed volume (and thus trigger the Quota Manager service to compare current disk volume with the quota for that volume), one of three things happens. First, if the object size reaches a threshold (by default, 90 percent of the quota limit, but you can configure this setting), the quota management service sends a message to the person who changed the size of the volume and to the owner of the quota. The service also writes an event to the Application log. Second, if the volume is below the threshold, nothing happens. Third, if the volume goes over quota with the write, the service logs the event and sends a message to anyone you've configured the service to notify. The quota management service takes ownership of the volume and edits its ACL to prevent writes (i.e., locks the volume). The administrator can manually unlock the volume, or Quota Manager unlocks it automatically when the user deletes enough files from the locked volume.

Installing Quota Manager is simple. At minimum, you must install the Quota Manager service on every server with quotas, and the administration tool on the server from which you configure quotas. Both installation wizards are simple to use, and you don't need to reboot before you use the tool or run the service. If you either accept the defaults for the service account and quota group or create the defaults ahead of time, setup won't cause difficulties.

The administration tool is simple and straightforward. Using the tool, you can create, manage, and delete quotas on disk volumes; the granularity of your control depends on the permissions the file system supports. Because FAT supports only share-level permissions, FAT volumes can have quotas only on shared folders. NTFS supports both local and shared permissions on files and folders, so you can set quotas on local and networked files and folders. Quota Manager doesn't support per-user or per-group quotas; if you want to customize quotas for different people, you must configure different shares for them. You can't nest incompatible quotas (e.g., by giving a subfolder a larger quota than its parent has).

The administration tool works on any server with the Quota Manager service installed, so you can manage servers remotely. The only catch is the lack of a browse function—you have to know the name of the remote server you want to administer the first time you enter it. After you've connected to the remote server once, however, it will appear on the drop-down list.

Quota Manager comes with a couple of tools (both of which you must install separately) that clients can use to keep an eye on their quotas. The Inquiry Tool queries servers running the service and reports on the state of any network shares the client is connected to. This tool shows only network connections, not local volumes, so its usefulness to an administrator is limited. More useful to users and administrators—and better integrated with the OS—is the Windows Explorer add-on that you'll find in the installation CD-ROM's QmExpAddOn folder. After you install this tool on a server or client and reboot, the property sheet for each managed volume or file will have a new tab, as Screen 1 shows. Neither users nor administrators can configure quotas from this tab, but it's a good way to let users see how closely they're pushing their quota limits.

The Quota Manager CD-ROM also includes a Microsoft Access-like reporting tool that you can use to monitor quotas on a local or remote server. This tool draws constantly from the quota management tools to maintain an updated report of your system, using counters you define.

Quota Manager monitors and controls disk usage without problem, and the software is easy to configure. However, you have to work with Quota Manager, rather than make it work with you. The groups for which you can implement quotas are inflexible, representing either the membership of the quota group or all users with write permissions to the managed volume. The reporting feature includes no standard reports, so inexperienced users might have to experiment with field selection to produce the reports they need. Additionally, you can't configure quota settings on a per-user basis, but only on specified volumes. If you want to control how much disk space individual users use—not just how much total space all users use—you'll need to organize your users into home directories, then set quotas on those directories. Because each quota takes up space in the Registry, companies with many home directories could experience Registry bloat.

Another problem I found with Quota Manager is its inability to clean up after itself. After a blue screen of death that occurred after I started up the administration tool (which might have been coincidence, because it didn't happen again), I decided to reinstall the product. I uninstalled and reinstalled the application from the Add/Remove Programs applet in Control Panel, but when I looked in the Registry, the settings were still there, and when I reinstalled the tool, the quotas I'd set up before were as I'd set them. If I uninstall a tool, I want it to disappear, not wait for me to hand-clean the Registry.

Overall, I found Quota Manager useful and easy to use. However, the product's organization and the way it stores data mean that it will work best for smaller companies that require little flexibility in their quota systems and have few quotas. Unfortunately, Quota Manager is a bit pricey for small businesses, which might therefore be inclined just to upgrade to Win2K and get quota management with the OS.

QuotaAdvisor 4.0, Enterprise Edition
Whereas Quota Manager is straightforward—select a volume, choose a quota for that volume and the threshold at which the volume should be aware of getting full—QuotaAdvisor has many more options for quota types and sensitivities. New users might find this confusing at first; experienced users will like the flexibility.

QuotaAdvisor is the management component of W. Quinn's StorageCeNTral tool suite. Installing the product is simple. You must have a password-protected account with Administrator privileges that the program can use. If you're configuring QuotaAdvisor to work with email notification, then Microsoft Exchange Server email will also use this account. After installation, the QuotaAdvisor tool will appear in the Programs folder.

By default, whenever you start QuotaAdvisor, a wizard for creating, deleting, or monitoring quota objects will initialize. You can choose to set up quotas on any QuotaAdvisor or DiskWatcher server in a trusted domain, and on any volume within those servers. (DiskWatcher is a tool in the StorageCeNTral suite that monitors disk usage.)

After you set up an object, you configure it from QuotaAdvisor's main console. Configuration involves choosing quota type and size, setting one or more thresholds at which the user and administrator will receive notification that the quota is approaching, and perhaps applying a quota template to the object.

On FAT and NTFS volumes, you can set quotas in two modes. Absolute mode sets an absolute quota on an object, no matter who writes to the managed volume. Learn mode has two forms: directory learn can monitor creation of new subfolders and monitor subfolder size; user learn notices when new users create objects within a volume. You can use either or both Learn modes. On NTFS volumes, you have a third option: per-user or per-group quotas on NTFS volumes that note who owns a file object and base quotas on that ownership.

Thresholds determine what happens as the managed volume nears or exceeds quota. QuotaAdvisor supports up to five thresholds, each with the options that Screen 2 shows. At various thresholds, you can execute commands, run reports, send messages, or take advantage of other options. You can configure thresholds for a particular object, but you can't apply one object's threshold set to another object.

Templates let you apply to an object a predefined set of options that govern thresholds, determine whether the quota is absolute or relative to the size of the object, and apply the quota to particular users. For example, the 20% More than Used template sets the quota for the selected volume to 120 percent of the usage at the time you applied the template and triggers the quota at 70 percent, 90 percent, and 100 percent of that value. QuotaAdvisor comes with several predefined templates, and you can create and save custom templates.

QuotaAdvisor has several tools to help you manage quotas and keep track of quota usage. First, a built-in Windows Explorer interface lets administrators set, edit, or delete quotas from the pop-up menu. The tool also includes a Set Owner command with which administrators can change the owner of a file object. Second, a monitoring tool displays usage and quota types for the quota object you select, or for all objects on a server. Third, the reporting function lets you create reports (customized or predefined) and produce ASCII, HTML, or comma-delimited output.

One significant advantage is QuotaAdvisor's clear and flexible reporting style. Because QuotaAdvisor doesn't change file permissions, it reports that a quota was exceeded, not that a volume is read-only. Telling users that their home directory has become read-only is a Help desk call waiting to happen; however, if users know that they've exceeded their quotas, they should be able to figure out the problem and delete files as required. QuotaAdvisor notifies even Windows 9x that the disk is full, which prompts the user to delete unneeded files. (Win9x can't process a "you've exceeded your quota" message; that is, because Win9x clients aren't quota-aware, they can understand only a Disk Full message.)

QuotaAdvisor is flexible—so flexible that the product is a bit confusing at first. However, once you're used to the interface and the myriad places from which you can set quota object properties, you'll find the tool useful in managing disk space. The product is definitely for the enterprise, however, and not for someone trying to manage disk space in a five-person office. The price is right for quota-management software—you get a lot of bang for your buck. Although administrators who are new to quota management and can't spare time to learn how to use it might find this tool too complicated, administrators of large networks will find that the time they spend learning to use this tool pays off.