File System Specifics

Your goal in creating a multiboot system is to have all the operating systems coexist in such a manner that they will be capable of sharing files with each other. Nothing is more frustrating than realizing that you must reboot to retrieve a file, copy it to a floppy, and reboot again to copy into your other operating system. A little bit of knowledge about file systems can save you many headaches down the road.

Not all operating systems use hard disks in the same manner. There are several different file system formats out there, which determine how file space is allocated, where directory information is stored, and so forth. The problem is that each operating system has its own list of supported file system types. Table 31.1 lists the various file systems supported by the operating systems discussed in this chapter. Note that in the table, RO stands for read-only, RW stands for read/write, and NS stands for not supported. Be sure to read the footnotes for any operating system you want to use.

Table 31.1. Relationships Between File Systems and Operating Systems

OS	Fat16	Fat32	NTFS4	NTFS5	Extended2
MS-DOS 6.22	RW
Windows 95	RW	NS	RO[1]	RO[1]	RO[2]
Windows 95b	RW	RW	RO[1]	RO[1]	RO[2]
Windows 98	RW	RW	RO[1]	RO[1]	RO[2]
Windows NT 4.0	RW	NS[3]	RW[4]	RW[4]	RO[6]
Windows 2000	RW	RW	RW[7]	RW	RO[6]
Windows XP	RW[5]	RW	RW[7]	RW	RO[6]
Linux	RW	RW	RO[8]	RO[8]	RW

^[1] Windows Me/9x can read the NTFS file system via a free utility called NTFS For Windows 98. Although NTFSWIN98 is read-only, it works very well and is highly recommended. A version with limited write capability can be purchased. You can obtain these products from http://www.sysinternals.com.

^[2] Windows Me/9x can gain read-only access to Linux's extended2 file system by using the free utility FSDEXT2. This utility can be found at http://www.yipton.demon.co.uk.

^[3] You can use the FAT32 utility for Windows NT 4.0 to read and write to FAT32 file systems from Windows NT 4.0. This utility can be obtained from http://www.sysinternals.com. This utility is not free.

^[4] If an NTFS partition is to be shared with Windows 2000 or XP, you must use Windows NT 4.0 Service Pack 4 or later.

^[6] Windows NT 4.0, Windows 2000 and Windows XP can read extended2 file systems by using the free utility Explore2FS. This utility can be found at http://uranus.it.swin.edu.au/~jn/linux/explore2fs.htm.

^[7] Windows 2000 and XP automatically convert NTFS version 4 volumes to NTFS version 5.

^[5] You can't format a new partition with FAT16 during XP's installation process or disk manager. Another OS must create it.

^[8] Although Linux kernels from 2.2.x on up provide a read/write driver for NTFS, you should use the driver only in read-only mode. The write portion of the NTFS driver is still in the very early stages of development and is safe to use only under very limited circumstances (see linux-ntfs.sourceforge.net).

Understanding the interplay between these various file systems is key in creating an efficient multiboot system. To the greatest extent possible, you should choose a format that's compatible with all the operating systems you'll want to use, on at least one disk partition. This will give a place to store files that can be read no matter which OS you're using.

Where you have the choice of several different candidate file systems, you must decide which is best, based on your hardware and the application for which you are creating your multiboot system. The following sections quickly recap file system descriptions, with an eye toward multibooting issues.

FAT16

FAT16 is the oldest file system mentioned in this chapter. It was originally intended for file systems based on the DOS operating system. As such, it is quite antiquated and not often used today. FAT16 might be your only choice in some situations due to its two major advantages:

• FAT16 is supported by almost all operating systems, including all versions of Windows, OS/2, MS-DOS, and Linux. FAT16 is the only format supported by MS-DOS 6.22 and earlier.

• The structure of the FAT16 file system is much simpler than the others, giving it much less software overhead. This gives FAT16 increased speed on volumes less than 1GB in size.

One big limitation of FAT16 is the fact that it cannot be installed in primary partitions greater than 2GB in size with MS-DOS and Windows 9x/Me; 4GB is the limit for FAT16 with Windows NT/2000/XP. To use the full capacity of a disk beyond those limits, an extended partition can be created, but it must be broken into non-bootable logical drives of no more than 2GB/4GB in size each. For example, a 10GB drive prepared as a FAT16 drive for use with both Windows Me and Windows XP would need to be divided into five drive letters, C: through G:. Also, the larger the partition, the less efficient FAT16 is in allocating space to small filesmore disk space is wasted. As explained later in the chapter, this limitation has been overcome by FAT16's new brother, FAT32.

NOTE

If you are using the first edition of Windows 95, you can use only the FAT16 file system. Versions of Windows 95 prior to Windows 95 OSR2 cannot use FAT32 partitions. A prompt upgrade to Windows 98 is recommended for this as well as for many other reasons.

Also, keep in mind that Microsoft frequently uses the term FAT to refer to both FAT16 and FAT32 file systems. The Disk Management program, in particular, only formats hard drive partitions with FAT32, not FAT16.

FAT32

The FAT32 file system was introduced with Windows 95 OSR2. FAT32 was essentially the answer to most of the shortcomings of FAT16. The following are among FAT32's strengths:

• FAT32 supports partitions up to 2TB in size (that's 2,048GB to you and me).

• FAT32 increased the number of clusters (decreasing the cluster size) on the hard disk, making the storage of small files take up less room than it did previously with FAT16.

• The structure of FAT32 remains very small, providing a notable speed increase over FAT16.

Of course, with all changes come pain and compatibility issues. To this day, Windows NT 4.0 does not natively support FAT32. The addition of FAT32 file support into Windows 2000 and XP is a welcome one, especially for multibooting users. However, neither FAT versions support the advanced security and reliability features of NTFS, as explained in the following section.

The versions of MS-DOS that ran underneath Windows 95 OSR2, 98, and Me can read and write FAT32 partitions, so you can use the command line mode of these operating systems if you need MS-DOS access to FAT32 partitions. The "standalone" versions of MS-DOS up to and including Version 6.22 cannot use FAT32 partitions.

NTFS

The New Technology File System, or NTFS, brought with it many welcome additions to the world of Microsoft computing, including the following:

• Permissions NTFS brought with it a concept used in the Novell and Unix worlds for quite some time. Permissions enable you to configure files and folders to be accessible only by specific users, user groups, or both. This is imperative for networked multiuser operating systems.

• Compression You can transparently compress folders or files on an NTFS volume.

• Reliability NTFS is much more reliable, and as such is suited to a server environment. Disk repair applications seldom need to be run on an NTFS file system.

• Large volumes are accessed much quicker with NTFS Although FAT still rules the below-1GB world, NTFS excels at accessing files and folders in very large disk partitions.

• Encryption came with the version of NTFS supplied with Windows 2000 and XP (also known as NTFS 5). Now you can lock individual files or folders for high levels of security.

• Dynamic disk arrangements enable you to group separate physical drives into one large virtual drive (see Chapter 29, "Managing the Hard Disk," for a full discussion). However, be careful with dynamic disksonly Windows 2000 and XP Professional support it, and other operating systems can't boot from a drive that's been set up for dynamic disk partitions.

A disadvantage of NTFS, however, is that it can't be read directly by DOS, OS/2, UNIX, or Windows Me/9x. You can download a free utility to read NTFS disks from http://www.sysinternals.com, and you can purchase a program with limited writing ability. Still, this isn't as straightforward as having support built into the operating system. Likewise, Linux has only limited support for NTFSreading works but writing is dangerous. So, NTFS is not a generally useful format for a shared partition on multiboot systems.

By the way, there are now two versions of NTFS: versions 4 and 5. Version 4 was used by Windows NT version 4.0. The updated version 5 is used by Windows 2000 and XP and supports additional capabilities such as encrypted files and dynamic disk partitions that can be rearranged while Windows is running. These capabilities aren't directly accessible with XP Home Edition, but Home Edition still uses the newer disk format.

The version difference will only affect you if you share an NTFS-formatted disk volume between Windows NT 4.0 and Windows XP or 2000. The newer OSes will update your NTFS partitions to version 5, so you must update Windows NT 4.0 to Service Pack 4 or later so that it can read the new format.