The Logical Disk Manager (LDM) is an implementation of a logical volume manager for Microsoft Windows NT, developed by Microsoft and Veritas Software. It was introduced with the Windows 2000 operating system, and is supported in Windows XP, Windows Server 2003, Windows Vista, Windows 7, Windows 8, Windows 10 and Windows 11. The MMC-based Disk Management snap-in (diskmgmt.msc) hosts the Logical Disk Manager. On Windows 8 and Windows Server 2012, Microsoft deprecated LDM in favor of Storage Spaces. Logical Disk Manager enables disk volumes to be dynamic, in contrast to the standard basic volume format. Basic volumes and dynamic volumes differ in their ability to extend storage beyond one physical disk. Basic partitions are restricted to a fixed size on one physical disk. Dynamic volumes can be enlarged to include more free space - either from the same disk or another physical disk. (For more information on the difference, see Basic and dynamic disks and volumes, below.)

Overview

Basic storage involves dividing a disk into primary and extended partitions. This is the route that all versions of Windows that were reliant on DOS-handled storage took, 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 (excluding versions such as Windows XP Home Edition, and Windows Vista Home Basic and Premium ), FreeBSD, 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. Only server versions of Windows (Windows Server) can support RAID5 feature of LDM.

Partition table types

On a disk partitioned with the MBR Partition Table scheme, the Logical Disk Manager metadata are not stored in a partition, but are stored in a 1 MB area at the end of the disk that is not assigned to any partition. The disc partitioning tools in Windows 2000 up to Windows 10 will not use that area for disk partitions, but the tools in other operating systems might. The aforementioned reservation of 1 MB would only occur on a disk which is identified by Windows as a "Local Disk" as opposed to a "Removable Disk". Thus a CompactFlash (CF) card capable of true IDE mode connected to a PC running Windows through an IDE port or a USB to ATA bridge, a mobile HDD enclosure case for instance, would get this reservation in contrast to one being connected through a normal USB card reader or a passive 16-bit CF to PCMCIA adapter where it does not deserve this reservation.

Basic and dynamic disks and volumes

Dynamic disk is a proprietary format of Microsoft developed together with Veritas. A basic volume is a volume stored on a basic disk, while a dynamic volume is a volume stored on a dynamic disk. Basic volumes and dynamic volumes differ in ability to extend storage beyond one physical disk. The basic partitions are confined to one disk and their size is fixed. Dynamic volumes allow to adjust size and to add more free space either from the same disk or another physical disk. Striped volumes (RAID 0) and spanned volumes (SPAN) are dynamic volumes using space on different physical disks. In Windows XP, spanned volume can use a maximum of 32 physical disks. The main differences between basic and dynamic disks are: Dynamic disks allow more flexible configuration without the need to restart the system. Some space at the end of the disk is reserved by the setup program of Windows with a kernel version of 5.x lest the disk would be upgraded to a dynamic one. The amount that is reserved is one cylinder or 1 MB, whichever is greater. One cylinder depending on drive geometry and translation can be up to 8 MB (to be precise, 512 bytes/sector × 63 sectors/head × 255 heads/cylinder = 8225280 bytes = 7.844 MiB) which account for a remaining 8 MB free space once Windows setup is used to create a partition. Coincidentally, Solaris 11 leaves exactly this amount of space at the beginning of a disk. Furthermore, this is not true since Windows Vista which always leaves 1 MB that is aligned to 2048 sector boundaries at the end of a local disk for the purpose of dynamic disk.

Compatibility problems

Disk Management in Windows Vista creates partitions according to a 1-MB alignment boundary, ignoring the previous conventions called "drive geometry" or "CHS". In other words, Vista's Disk Management acts like it is using a non-standard CHS geometry of 2048 sectors per track/head and 1 track/head per cylinder (the sectors being of 512 bytes so that 2048 sectors is 1 MB).

Compatibility problems with using a 1-MB alignment boundary

Advantages of using a 1-MB alignment boundary