Local File Systems for Windows
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Local File Systems for Windows WinHEC 2004 Version—May 5, 2004 Abstract This paper provides information about local file systems for the Microsoft® Windows® family of operating systems. It provides guidelines to help system manufacturers and server administrators choose the local file system that is best suited for a particular use and media type. This information applies for the following operating systems: Microsoft Windows 98 Microsoft Windows 2000 Microsoft Windows XP Microsoft Windows Server™ 2003 Microsoft Windows Vista™ The current version of this paper is maintained on the Web at: http://www.microsoft.com/whdc/device/storage/default.mspx Contents 1 Introduction .................................................................................................................... 3 2 Local File System Overview .......................................................................................... 3 2.1 About the FAT File System .................................................................................. 3 2.2 About the NTFS File System................................................................................ 5 2.3 About the UDF File System ................................................................................. 6 3 Local File System Feature Comparison ......................................................................... 8 4 Local File System Limitations ........................................................................................ 9 4.1 File System Limits Imposed by the File System Format .................................... 10 4.2 File System Limits Imposed by the File System Driver ...................................... 11 5 Resources and Call to Action ...................................................................................... 15 5.1 Call to Action ...................................................................................................... 15 5.2 Feedback ........................................................................................................... 15 5.3 Resources .......................................................................................................... 15 6 Appendix—Glossary .................................................................................................... 16 ¡Error! Utilice la ficha Inicio para aplicar Title al texto que desea que aparezca aquí. - 2 Disclaimer This is a preliminary document and may be changed substantially prior to final commercial release of the software described herein. The information contained in this document represents the current view of Microsoft Corporation on the issues discussed as of the date of publication. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information presented after the date of publication. This White Paper is for informational purposes only. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS DOCUMENT. Complying with all applicable copyright laws is the responsibility of the user. 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Utilice la ficha Inicio para aplicar Title al texto que desea que aparezca aquí. - 3 1 Introduction This paper describes the features, benefits, and architectural limits of three local file systems currently supported on the Microsoft® Windows® 98, Microsoft Windows XP, Microsoft Windows 2000, Microsoft Windows Server™ 2003, and Microsoft Windows Vista platforms: File Allocation Table (FAT) NTFS Universal Disk Format (UDF) There are many important factors that must be considered when selecting a local file system format. This paper is intended to provide system manufacturers and server administrators with the necessary information to choose the local file system that is best suited for a particular usage scenario and media type. This paper assumes basic knowledge of local file systems. For a description of the terminology used in this paper, see Appendix A—Glossary. This paper includes the following sections: Local File System Overview: Provides an overview for each of the three local file systems and describes usage scenarios for each type of local file system. Local File System Limitations: Provides information about the limits imposed by the on-disk structures and those imposed by the Windows file system driver implementation for each of the file systems. 2 Local File System Overview Over the past 25 years, as PCs have become more powerful and storage media, such as hard disk drives, have become exponentially larger, the demand for local file systems that store larger file sizes and quantities of files has emerged. At the same time, there is an increasing demand for removable media, such as Flash and CD/DVD media. These media types are being used on PCs, as well as consumer electronic devices, to provide mobility of data. As PCs have moved into the enterprise space that serves a variety of purposes, including file share servers, mail servers, and database servers, the need has also arisen for robust local file systems with advanced features, such as recoverability, availability, security, and performance. These demands have made it necessary to choose the appropriate file system that meets the unique requirements of each of the usage scenarios. This section provides history and feature overview information about the NTFS, FAT, and UDF file systems and describes the media on which each of these three local file systems is best suited. 2.1 About the FAT File System The FAT file system originated in the late 1970s and early1980s and was the file system supported by the Microsoft MS-DOS® operating system. It was originally developed as a simple file system suitable for floppy disk drives less than 500 KB in size. Over time it has been enhanced to support larger and larger media. Currently there are three FAT file system types: FAT12, FAT16, and FAT32. The basic difference in these FAT sub types, and the reason for the names, is the size (in bits) of the FAT entries in the actual FAT structure on the disk. The following table shows WinHEC 2004 Version—May 5, 2004 © 2004 Microsoft Corporation. All rights reserved. ¡Error! Utilice la ficha Inicio para aplicar Title al texto que desea que aparezca aquí. - 4 the number of bits used in the FAT entry for each FAT file system type and what each type is used for in Windows. Table 2—UDF versions supported by Windows FAT type Bits in the Uses FAT entry FAT12 12 Current versions of Windows use FAT12 for floppy disk media and removable media. FAT16 16 Windows supports FAT16 for hard disk volumes and removable media. FAT32 32 Windows supports FAT32 for hard disk volumes and removable media. For information about the size limits for FAT16 and FAT32 hard disk volumes, see the “Local File System Limitations” section of this paper. 2.1.1 Media Suitable for FAT The FAT file system is ideal for removable Flash media that is used in consumer electronic devices, such as digital cameras, media players, Flash drives, and so on. FAT12 is, of course, the only file system that can be used on floppy disks. Note: The FAT file system is ideal for use with devices that are optimized for quick media removal. 2.1.1.1 What Makes FAT Suitable for These Media The following list provides reasons why the FAT file system is suitable for devices like memory sticks and floppy disk drives: Consumer electronics device friendly: FAT is a light-weight file system that is simple and easy to implement. Backward compatibility: FAT 12 and FAT 16 are recognized by all operating systems from MS-DOS forward. FAT 32 is recognized by all operating systems from Windows 98 forward. This backward compatibility enables the use of memory stick media or floppy disks to transfer files between a consumer electronics device and a PC that is running an out-dated operating system. No unnecessary features: FAT is not a journaled file system and is not as reliable as NTFS. However, because these