Logical Disk Manager (LDM) Overview
Dynamic disks provide features that basic disks do not, such as the ability to create volumes that span multiple disks (spanned and striped volumes), and the ability to create fault tolerant volumes (mirrored and RAID-5 volumes). All volumes on dynamic disks are known as dynamic volumes.
There are five types of dynamic volumes:
- Simple
- A dynamic volume made up of disk space from a single dynamic disk. A simple volume can consist of a single region on a disk or multiple regions of the same disk that are linked together. If the simple volume is not a system volume or boot volume, you can extend it within the same disk or onto additional disks. If you extend a simple volume across multiple disks, it becomes a spanned volume. You can create simple volumes only on dynamic disks. Simple volumes are not fault tolerant, but you can mirror them to create mirrored volumes on computers running the Windows 2000 Server or Windows Server 2003 families of operating systems.
- Spanned
- A dynamic volume consisting of disk space on more than one physical disk. You can increase the size of a spanned volume by extending it onto additional dynamic disks. You can create spanned volumes only on dynamic disks. Spanned volumes are not fault tolerant and cannot be mirrored.
- Striped
- A dynamic volume that stores data in stripes on two or more physical disks. Data in a striped volume is allocated alternately and evenly (in stripes) across the disks. Striped volumes offer the best performance of all the volumes that are available in Windows, but they do not provide fault tolerance. If a disk in a striped volume fails, the data in the entire volume is lost. You can create striped volumes only on dynamic disks. Striped volumes cannot be mirrored or extended.
- Mirrored
- A fault-tolerant volume that duplicates data on two physical disks. A mirrored volume provides data redundancy by using two identical volumes, which are called mirrors, to duplicate the information contained on the volume. A mirror is always located on a different disk. If one of the physical disks fails, the data on the failed disk becomes unavailable, but the system continues to operate in the mirror on the remaining disk. You can create mirrored volumes only on dynamic disks on computers running the Windows 2000 Server or Windows Server 2003 families of operating systems. You cannot extend mirrored volumes.
- RAID-5
- A fault-tolerant volume with data and parity striped intermittently across three or more physical disks. Parity is a calculated value that is used to reconstruct data after a failure. If a portion of a physical disk fails, Windows recreates the data that was on the failed portion from the remaining data and parity. You can create RAID-5 volumes only on dynamic disks on computers running the Windows 2000 Server or Windows Server 2003 families of operating systems. You cannot mirror or extend RAID-5 volumes. In Windows NT 4.0, a RAID-5 volume was known as a striped set with parity.
Mirrored and RAID-5 volumes are fault tolerant and are available only on computers running Windows 2000 Server, Windows 2000 Advanced Server, Windows 2000 Datacenter Server, or the Windows Server 2003 family of operating systems. You can, however, use a computer running Windows XP Professional to remotely create mirrored and RAID-5 volumes on these operating systems.
Regardless of whether the dynamic disk uses the master boot record (MBR) or GUID partition table (GPT) partition style, you can create up to 2,000 dynamic volumes, although the recommended number of dynamic volumes is 32 or less.
