Logical Disk Manager
From Wikipedia, the free encyclopedia
The Logical Disk Manager is an implementation of a logical volume manager for Microsoft Windows, developed by Microsoft and Veritas Software. It was introduced with the Windows 2000 operating system, and is supported in Windows XP, Windows Server 2003 and Windows Vista.
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[edit] Overview
Basic storage involves dividing a disk into primary and extended partitions.[1] This is the way that all versions of Windows that were reliant on DOS handled storage, and disks formatted in this manner are known as basic disks. Dynamic storage involves the use of a single partition that covers the entire disk, and the disk itself is divided into volumes or combined with other disks to form volumes that are greater in size than one disk itself. Volumes can use any supported file system.
Basic disks can be upgraded to dynamic disks, however when this is done the disk cannot easily be downgraded to a basic disk again. To perform a downgrade, data on the dynamic disk must first be backed up onto some other storage device. Second, the dynamic disk must be re-formatted as a basic disk (erasing all data). Finally, data from the backup must be copied back over to the newly re-formatted basic disk.
Dynamic disks provide the capability for software implementations of RAID. The main disadvantage of dynamic disks in Microsoft Windows is that they can only be recognized under certain operating systems, such as Windows 2000 or later, or the Linux kernel starting with version 2.4.8.
Dynamic disks under Windows are provided with the use of databases stored on disk(s). The volumes are referred to as dynamic volumes. It is possible to have 2000 dynamic volumes per dynamic disk, but the maximum recommended by Microsoft is 32.
[edit] Partition table types
| ID (GUID Partition Table and MBR Partition Table) | Description |
|---|---|
GPT: 5808C8AA-7E8F-42E0-85D2-E1E90434CFB3MBR: None1 |
"metadata" partition. The area of the disc that is used for holding configuration data that describe the volumes that LDM manages. |
GPT: AF9B60A0-1431-4F62-BC68-3311714A69ADMBR: 0x42 |
"data" partition. The area of the disc that is used for holding LDM volumes themselves. |
Note 1: On a disc partitioned with the MBR Partition Table scheme, the Logical Disk Manager metadata are not stored in a partition, but are stored in a 1MiB area at the end of the disc that is not assigned to any partition[2]. The disc partitioning tools in Windows XP will not use that area for disc partitions, but the tools in other operating systems might.
[edit] References
- ^ How Basic Disks work. Microsoft TechNet.
- ^ How Dynamic Disks work. Microsoft TechNet.
