Before you can use a hard disk or a floppy disk, you must format the disk.
There are three steps to formatting a hard disk:
Formatting a floppy disk is much simpler than formatting a hard disk, because there are fewer steps. You cannot create partitions on a floppy disk, so there are only two steps:
When you format a floppy disk, the format program performs both a low-level format and a logical format, so there is really only one step. However, the low-level format on a floppy disk is not as thorough as on a hard disk.
The rest of this section discusses low-level formatting, creating primary partitions or volumes, and logical formatting. See the section "Which Programs to Use to Create and Format Volumes," presented earlier in this chapter, for more details.
Each disk vendor provides the low-level format program to use for the disk. Consult your disk documentation or contact the vendor to find out how to do low-level formatting.
Each low-level format program determines the correct sector size to use, the number of tracks, and the number of sectors per track. This format program selects sector size based upon the disk and the information about the sectors in its circuitry. The program for almost all disks used in the United States uses a sector size of 512 bytes. The program also writes error correction and sector identification information for each sector onto the disk.
SCSI disks should always be low-level formatted when put on a new controller. The reason for this is that the translation in use on the disk varies from controller to controller, and can even vary between two identical controllers based upon the controller settings.
On x86-based computers, you must enable the BIOS on the SCSI controller if your system partition in on a SCSI disk. Depending upon your disk configuration, you might need to turn off translation in the SCSI controller. Also make sure that the CMOS has no entries for SCSI disks. For more information about the SCSI controller, see Chapter 20, "Preparing for and Performing Recovery."
There are some older IDE disks that you should not low-level format, because the factory formatting puts information on the disk that a low-level format erases. However, newer IDE disks, and all enhanced IDE disks (also known as EIDE) need to be low-level formatted. You must configure an IDE or EIDE disk in the CMOS before you can use it on the computer. See your hardware documentation for information about changing information in the CMOS.
If you have created and formatted volumes on your hard disk, but are getting errors from Chkdsk or other disk scan utilities about bad sectors on your disk, the only way to permanently eliminate them is to do a low-level format. Low-level formatting maps around the bad sectors. However, a low-level format erases all data on the disk. Therefore, be sure to back up any data on the disk before you low-level format it. You then need to create volumes (primary partitions or logical drives in an extended partition), and logically format them before you can restore the data to the disk.
Caution Do not low-level format IDE hard disks unless the manufacturer's literature describes that you should do so.
When you create primary partitions or an extended partition on a disk, you logically divide it into one or more areas that can be formatted for use by a file system. The first partition on the disk (whether it is a primary partition or an extended partition) always starts at the outside of the disk, at cylinder 0, head 0, and sector 1. Because partition boundaries are always cylinder boundaries, the smallest partition that you can create on a disk consists of all of the tracks on a single cylinder.
When you have Windows NT installed on your computer, you should use Disk Administrator to create partitions. However, if you are setting up a new computer, you might not have any operating system. But you still need to create and format a partition into which to install Windows NT.
On x86-based computers, if you have an MS-DOS bootable floppy disk with the Fdisk program on it, you can start your computer from the MS-DOS floppy disk and create partitions by using Fdisk. On RISC-based computers, you can use the Arcinst program on the Windows NT Workstation CD to create partitions. Windows NT Setup displays an option to create a partition to use for Windows NT, provided that there is enough unpartitioned space on a hard disk.
Note
On x86-based computers, you might not be able to access all your hard disk when using fdisk. If you have a disk that is larger than 4 gigabyte (GB), MS-DOS cannot see the space beyond 4 GB. Depending on the geometry, this limitation could even be 1 GB, because MS-DOS cannot access volumes that go beyond cylinder 1023. If you have more than 2 SCSI disks, MS-DOS generally does not see any disks after the first two, unless you load a SCSI device driver.
When you create the first partition on a disk (either a primary partition or an extended partition), the program that you use creates the Master Boot Record and writes it to the first sector on the disk (cylinder 0, head 0, sector 1). The Master Boot Record contains the Partition Table, which has information about each partition defined on the disk. When you make any changes to volumes on the disk, such as creating, deleting, or formatting them, the program that you are using updates the Partition Table.
You can configure the entire disk as one primary partition, and logically format it for one file system. Or you can create more than one primary partition, and use different file systems on them. You can also create an extended partition, and create one or more logical drives within the extended partition.
For more information about partitions, logical drives, and extended partitions, see "Logical Organization: Partitions, Volumes, Volume Sets, and Stripe Sets," presented earlier in this chapter. For more information about the Master Boot Record and Partition Table, see "Disk Sectors Critical to the Startup Process," presented later in this chapter.
Before you can write any data to the volume, you must do a logical format; that is, format it for use by a file system. Logical formatting writes information needed by the file system onto the disk. The information includes:
There is more information about each of these data in the remainder of this chapter.
When you have Windows NT installed on your computer, you should use Disk Administrator to format the partitions.
On x86-based computers, you can format primary partitions and logical drives for the FAT file system before you install any operating systems by starting the computer from a MS-DOS bootable floppy disk that has the Format program on it. You can use the Format program only for volumes that do not go beyond cylinder 1023.
On Alpha-based computers and MIPS-based computers, you can run the Arcinst program from the Windows NT Workstation CD to format the hard disk.
On both x86-based computers and RISC-based computers, you can create and format a primary partition to use for Windows NT during Setup, provided that there is enough unpartitioned space on a hard disk.