Working with the UDF File System

Monday Feb 5th 2001 by Brien M. Posey

Windows 2000 supports the Universal Disk Format, which goes beyond the capabilities of FAT, NTFS, and other file systems you may be more familiar with.

If you've been working with Windows NT and Windows 2000 for a while, you're probably familiar with the FAT 16, FAT 32, CDFS, HPFS, and NTFS file systems. However, Windows 2000 supports another file system that you might not be aware of: Universal Disk Format (UDF). In this article, I'll introduce you to the UDF file system. As I do, I'll explain the file system's capabilities and the benefits of using UDF.

Understanding Clusters

Before you can appreciate the way UDF works, you must understand how clusters work. A cluster is the smallest possible unit of hard disk storage. Clusters range in size depending on the size of the hard disk and the file system used. However, regardless of the size of the cluster, even a one-byte file consumes an entire cluster. Therefore, if you save a one-byte file on a hard disk that has a 16KB cluster size, the file will consume the entire 16KB.

Larger files span multiple clusters. For example, if you save a 34KB file on a hard disk that uses 16KB clusters, the file will consume 48KB. The first 32KB is stored in the first two clusters, which are completely used. However, the remaining 2KB will be placed in the last cluster. So, 2KB of the last cluster is used and 14KB is wasted.

How UDF Works

As you can imagine, having a large cluster size can result in a lot of wasted hard disk space. Therefore, the trick to getting back some of your hard disk space is to reduce the cluster size. Converting a hard disk from FAT 16 to FAT 32 reduces cluster sizes and can also allow the drive to exceed FAT 16's 2GB limit. Unfortunately, not all versions of Windows support FAT 32. Only some Windows 95 releases supported FAT 16, and Windows NT doesn't support FAT 16 at all (without a third-party patch).

The UDF file system offers the best of both worlds. It is designed to reduce cluster sizes, while working with all versions of Windows since Windows 95.

Formatting in UDF

Unfortunately, although Windows 2000 supports the UDF format, it doesn't offer you the chance to format a hard disk in UDF format. For now, the UDF file format is typically used for rewritable DVDs. Before you can save data to a DVD-RAM disk, the media must be formatted. Although you can format a DVD-RAM disk in a variety of formats, UDF is the preferred choice because of its versatility.

Because Windows 2000 doesn't offer UDF formatting capabilities, you'll have to use a third-party add-on to accomplish this task. I personally use a utility called Format UDF. Format UDF is included with a software package called Write DVD Pro For Windows, from Software Architects, Inc.. //

Brien M. Posey is an MCSE who works as a freelance writer. His past experience includes working as the director of information systems for a national chain of health care facilities and as a network engineer for the Department of Defense. Because of the extremely high volume of e-mail that Brien receives, it's impossible for him to respond to every message, although he does read them all.

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