Volumes and Disks

Hard Drive Partitions A hard drive may be split into partitions. NT uses two main partitions but I believe these two may be installed on one partition. There can be up to 4 primary partitions and only one extended partition which may include several logical drives. A logical drive is assigned its own drive letter and uses part of or all the space in an extended partition. Only one partition may be extended and an extended partition may not be marked as active which means operating systems cannot be booted from it. Only one partition on a disk may be active at a time. On IBM compatible computers, only a primary partition may be a system partition which is where the NT boot loader must reside. Windows 2000 Logical Partitions Windows 2000 logical partitions include: System - Stores system files for booting such as NTLDR, BOOT.INI, and NTDETECT.COM. Boot - WINNT_Root partition where system files are. These partitions may be on the same or on separate physical hard drive partitions. The filesystem containing the boot files is referred to as the system partition and the partition that contains the WINNT40 directory is the boot partition. Windows Disk Types Windows uses the below two terms to refer to disks in a computer. Basic Disks - A standard disk with standard partitions (primary and extended). Dynamic Disks - Disks that have dynamic mounting capability to add additional local or remote partitions or directories to a disk drive. These are called dynamic volumes. This is new with the Windows 2000 operating system and is not supported by any other operating systems. Any volume that is on more than one hard drive must be created with dynamic disks. A disk can only be converted from dynamic to basic by first deleting all the volumes in the dynamic disk.

Windows NT Volume Sets

A Windows NT volume may span several partitions and includes:

• The disk directory area also called the root directory.
• Allocation tables to track used disk space.

Characteristics and limitations:

• A volume may contain 1 to 32 disk areas and can be formatted as FAT or NTFS.
• These combined areas cannot be split or one part of a volume can't be deleted without destroying the entire volume.
• They may contain disk areas from various drive types such as IDE or SCSI.
• NT system and boot partitions cannot be part of a volume set. Windows 95 and DOS don't recognize volume sets.

Volume sets (which are on basic disks) created with Windows NT are supported by Windows 2000 but may not be created with Windows 2000.

Windows 2000 supports the following types of volumes which can only be created on dynamic disks:

• Simple Volumes - Formatted partition on a hard drive. Has no fault tolerance.
• Spanned Volumes - Formatted partition or disk space on more than one partition or hard drive that appears as one volume. In Windows NT, this is called a volume set. Has no fault tolerance. The system or boot partitions cannot be included in a spanned volume. FAT, FAT32 and NTFS file systems may be included. Space from two to thirty two dynamic disks can be included. If one disk on the spanned volume fails, all data is lost, and no part of a spanned volume may be removed without destroying the entire volume.
• Striped Volumes - Also called disk stripingor a striped set in Windows NT, it is when two areas of disk space which are identical in size have half the information written on one area and the other half written on the second area. This effectively doubles the disk access speed, but provides no fault tolerance. In Windows NT, this is called a stripe set which is created on a basic disk.
• Mirrored Volumes - Also known as RAID 1 or a mirror set on Windows NT, this is a fault tolerance method where data is stored on two volumes (that appear as one) rather than a single volume. This costs access time, but is fault tolerant.
• RAID-5 Volumes - Require three or more areas of formatted drive space. Generating parity information can cost processor time.

Mirrored volumes and RAID-5 volumes are not supported by Windows 2000 Professional. Other than sector fixing, there is no fault tolerance provided with Windows 2000 Professional. For a certification test, fault tolerance is not provided with Windows 2000 Professional.

Stripe Sets

A stripe set is established using free space from between 2 and 32 physical hard drives. The free space on each drive must be the same capacity. Data is written is 64k blocks simultaneously on each drive in the stripe set which increases disk drive read and write access speed. Windows 2000 Professional supports stripe sets, but not stripe sets with parity. Windows 2000 Professional does not support disk drive fault tolerance, only supporting stripe sets without parity and sector sparing.

NT system and boot partitions cannot be part of a stripe set.

Other Windows 2000 fault tolerant options include:

• RAID 5 or stripe sets with a parity drive.
• Disk mirroring
• Sector hot fixing

Other Windows 2000 file and filesystem characteristics that enhance file storage:

• Confirmation that hard drive write requests were done.
• Disk cache is used to store data going to or from the disk to speed up access time. This is referred to as lazy writing.
• Hard links are used to tie file physical location to multiple file names.