The Logical Disk Manager (LDM) is an implementation of a
logical volume manager
In computer storage, logical volume management or LVM provides a method of allocating space on mass-storage devices that is more flexible than conventional partitioning schemes to store volumes. In particular, a volume manager can concatenate ...
for
Microsoft Windows NT
Windows NT is a proprietary graphical operating system produced by Microsoft, the first version of which was released on July 27, 1993. It is a processor-independent, multiprocessing and multi-user operating system.
The first version of Win ...
, developed by
Microsoft
Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...
and
Veritas Software
Veritas Technologies LLC. is an American international data management company headquartered in Santa Clara, California. The company has its origins in Tolerant Systems, founded in 1983 and later renamed Veritas Software. It specializes in stor ...
. It was introduced with the
Windows 2000
Windows 2000 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. It was the direct successor to Windows NT 4.0, and was Software release life cycle#Release to manufacturing (RTM), releas ...
operating system, and is supported in
Windows XP
Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct upgrade to its predecessors, Windows 2000 for high-end and ...
,
Windows Server 2003
Windows Server 2003 is the sixth version of Windows Server operating system produced by Microsoft. It is part of the Windows NT family of operating systems and was released to manufacturing on March 28, 2003 and generally available on April 24, 2 ...
,
Windows Vista
Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, which was released five years before, at the time being the longest time span between successive releases of ...
,
Windows 7
Windows 7 is a major release of the Windows NT operating system developed by Microsoft. It was released to manufacturing on July 22, 2009, and became generally available on October 22, 2009. It is the successor to Windows Vista, released nearly ...
,
Windows 8
Windows 8 is a major release of the Windows NT operating system developed by Microsoft. It was Software release life cycle#Release to manufacturing (RTM), released to manufacturing on August 1, 2012; it was subsequently made available for downl ...
,
Windows 10
Windows 10 is a major release of Microsoft's Windows NT operating system. It is the direct successor to Windows 8.1, which was released nearly two years earlier. It was released to manufacturing on July 15, 2015, and later to retail on J ...
and
Windows 11
Windows 11 is the latest major release of Microsoft's Windows NT operating system, released in October 2021. It is a free upgrade to its predecessor, Windows 10 (2015), and is available for any Windows 10 devices that meet the new Windows 11 ...
. The
MMC-based ''Disk Management'' snap-in () hosts the Logical Disk Manager. On Windows 8 and
Windows Server 2012
Windows Server 2012, codenamed "Windows Server 8", is the sixth version of the Windows Server operating system by Microsoft, as part of the Windows NT family of operating systems. It is the server version of Windows based on Windows 8 and succe ...
, Microsoft deprecated LDM in favor of
Storage Spaces
The transition from Windows 7 to Windows 8 introduced a number of new features across various aspects of the operating system. These include a greater focus on optimizing the operating system for touchscreen-based devices (such as tablet compute ...
.
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
partition
Partition may refer to:
Computing Hardware
* Disk partitioning, the division of a hard disk drive
* Memory partition, a subdivision of a computer's memory, usually for use by a single job
Software
* Partition (database), the division of a ...
s. This is the route that all versions of Windows that were reliant on
DOS
DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems.
DOS may also refer to:
Computing
* Data over signalling (DoS), multiplexing data onto a signalling channel
* Denial-of-service attack (DoS), an attack on a communicat ...
-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
In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one larg ...
.
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
Raid, RAID or Raids may refer to:
Attack
* Raid (military), a sudden attack behind the enemy's lines without the intention of holding ground
* Corporate raid, a type of hostile takeover in business
* Panty raid, a prankish raid by male college ...
. The main disadvantage of dynamic disks in Microsoft Windows is that they can only be recognized under certain operating systems, such as
Windows 2000
Windows 2000 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. It was the direct successor to Windows NT 4.0, and was Software release life cycle#Release to manufacturing (RTM), releas ...
or later (excluding versions such as
Windows XP
Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct upgrade to its predecessors, Windows 2000 for high-end and ...
Home Edition, and
Windows Vista
Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, which was released five years before, at the time being the longest time span between successive releases of ...
Home Basic and Premium),
FreeBSD
FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular ...
, or the
Linux
Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...
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.
Partition table types
On a disk partitioned with the MBR Partition Table scheme, the Logical Disk Manager
metadata
Metadata is "data that provides information about other data", but not the content of the data, such as the text of a message or the image itself. There are many distinct types of metadata, including:
* Descriptive metadata – the descriptive ...
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
CompactFlash (CF) is a flash memory mass storage device used mainly in portable electronic devices. The format was specified and the devices were first manufactured by SanDisk in 1994.
CompactFlash became one of the most successful of the e ...
(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
The Personal Computer Memory Card International Association (PCMCIA) was a group of computer hardware manufacturers, operating under that name from 1989 to 2009. Starting with the PCMCIA card in 1990 (the name later simplified to ''PC Card''), i ...
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. Presently, spanned volume can use a maximum of 32 physical disks.
The main differences between basic and dynamic disks are:
* Dynamic disks support multi-partition volumes; basic disks do not.
* Windows stores basic disk partition information in the registry and dynamic disk partition information on the disk
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 MB) which account for a remaining 8 MB free space once Windows setup is used to create a partition. Coincidentally,
Solaris 11
Solaris may refer to:
Arts and entertainment Literature, television and film
* ''Solaris'' (novel), a 1961 science fiction novel by Stanisław Lem
** ''Solaris'' (1968 film), directed by Boris Nirenburg
** ''Solaris'' (1972 film), directed by ...
leaves exactly this amount of space at the beginning of a disk. Furthermore, this is not true since
Windows Vista
Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, which was released five years before, at the time being the longest time span between successive releases of ...
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".
[ (Source is questionable. There is some confusion on this source page, which is clarified ]here
Here is an adverb that means "in, on, or at this place". It may also refer to:
Software
* Here Technologies, a mapping company
* Here WeGo (formerly Here Maps), a mobile app and map website by Here Technologies, Here
Television
* Here TV (form ...
.) In other words, Vista's Disk Management acts like it is using a non-standard CHS geometry of 2048
sector
Sector may refer to:
Places
* Sector, West Virginia, U.S.
Geometry
* Circular sector, the portion of a disc enclosed by two radii and a circular arc
* Hyperbolic sector, a region enclosed by two radii and a hyperbolic arc
* Spherical sector, a po ...
s per
track
Track or Tracks may refer to:
Routes or imprints
* Ancient trackway, any track or trail whose origin is lost in antiquity
* Animal track, imprints left on surfaces that an animal walks across
* Desire path, a line worn by people taking the shorte ...
/
head
A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may ...
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
*Extended partition tables that are edited with Vista Disk Management should not be edited with Windows XP Disk Management. XP Disk Management may delete these extended partitions without warning. One way to correct these mixed partition tables is to delete all partitions (reboot or reconnect drive) and use only one partition editor on the drive.
*You may not be able to install XP or Windows Server 2003 to partitions created with Vista Disk Management.
*These 1 MB alignments ignore prior
CHS conventions such as the regular intervals at which partitions begin and end, and the distance between the
extended boot record
An extended boot record (EBR), or extended partition boot record (EPBR), is a descriptor for a logical partition under the common DOS disk drive partitioning system. In that system, when one (and only one) partition record entry in the master boot ...
s and their
logical drive
In computer data storage, a volume or logical drive is a single accessible storage area with a single file system, typically (though not necessarily) resident on a single partition of a hard disk. Although a volume might be different from a physi ...
s.
:Other operating systems (perhaps
DOS
DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems.
DOS may also refer to:
Computing
* Data over signalling (DoS), multiplexing data onto a signalling channel
* Denial-of-service attack (DoS), an attack on a communicat ...
programs used by backup or recovery software), boot loaders, or
partitioner
A disk editor is a computer program that allows its user to read, edit, and write raw data (at ASCII, character or hexadecimal, byte, byte-levels) on disk drives (e.g., hard disks, USB flash disks or removable media such as a floppy disks); as suc ...
s may have problems viewing or editing partitions that do not follow a CHS alignment. (Generally, unpredictable results may come from using more than one partitioner on the same
partition table
Disk partitioning or disk slicing is the creation of one or more regions on secondary storage, so that each region can be managed separately. These regions are called partitions. It is typically the first step of preparing a newly installed disk, ...
without checking the alignments with tools such as
Ranish Partition Manager
Ranish Partition Manager is a freeware hard disk partition editor, disk cloning utility, and boot manager, that gives a high level of control for creating multi-boot systems. It is available on the freeware live CD SystemRescueCD and the Ultimat ...
. For example,
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...
installers usually start with a
partition editor so it may be important that this uses the same alignments as the previous partition editors, if all partitions are not deleted (and the computer reset) before installing the operating system. The variation in CHS geometry is almost always a different number of heads per cylinder, for example, 240 instead of 255. However, partition editors may seem to ignore this sort of geometry in some situations. "Head" and "track" mean the same thing in this context.)
Advantages of using a 1-MB alignment boundary
* Microsoft states that on
large-sector drives, also known as
advanced format
Advanced Format (AF) is any disk sector format used to store data on magnetic disks in hard disk drives (HDDs) that exceeds 512, 520, or 528 bytes per sector, such as the 4096, 4112, 4160, and 4224-byte (4 KB) sectors of an Advanced Format ...
, there is a "performance issue" (i.e., problem) when the starting offset of the first partition is an "odd" number. This partition alignment offset also affects newer generation drives not necessarily specified as
advanced format
Advanced Format (AF) is any disk sector format used to store data on magnetic disks in hard disk drives (HDDs) that exceeds 512, 520, or 528 bytes per sector, such as the 4096, 4112, 4160, and 4224-byte (4 KB) sectors of an Advanced Format ...
such as
SSD drives. Misalignment causes severe degradation not only with random write performance, but also with sequential write performance (normally to a far lesser degree).
:(Quoting Microsoft directly): "In earlier versions of Windows, the default starting
offset
Offset or Off-Set may refer to:
Arts, entertainment, and media
* "Off-Set", a song by T.I. and Young Thug from the '' Furious 7: Original Motion Picture Soundtrack''
* ''Offset'' (EP), a 2018 EP by singer Kim Chung-ha
* ''Offset'' (film), a 200 ...
for the first partition on a hard disk drive was sector 0x3F. Because this starting offset was an odd number, it could cause performance issues on large-sector drives because of misalignment between the partition and the physical sectors. In Windows Vista, the default starting offset will generally be sector 0x800."
::The "starting offset" refers to the sectors before the partition. "3F" is a hexadecimal value; in decimal that is "63". This is the size of one head (or "track") in terms of a standard
CHS geometry. The hex value "800", in decimal form is 2048, so this is referring to the first
MB of space, from the start of the disk. Because a 1-MB alignment boundary is used by the Vista partitioner(s), 1 MB is "reserved for" the
Master boot record
A master boot record (MBR) is a special type of boot sector at the very beginning of partitioned computer mass storage devices like fixed disks or removable drives intended for use with IBM PC-compatible systems and beyond. The concept of MBR ...
(MBR), instead of the traditional 63 sectors (31.5
KB). Note that the MBR is only one sector in size, but many software packages use these 63 sectors of "free space" (or any "free space" preceding the partition) for their purposes. 63 sectors is the minimum space that should be reserved for the MBR or an
Extended Boot Record
An extended boot record (EBR), or extended partition boot record (EPBR), is a descriptor for a logical partition under the common DOS disk drive partitioning system. In that system, when one (and only one) partition record entry in the master boot ...
(EBR).
::What this means is that, if there were no partitions on a disk when it was booted, a partition was created using standard CHS geometry (as would be used by most partition editors such as DOS fdisk, Linux fdisk, Ranish Partition Manager, or an XP installation disk), and this partition was created at the start of the disk, then the partition will start on the 2nd head. The partition could not begin at the first sector because the MBR located there, so instead it starts the partition on the second head. When primary partitions are created anywhere else (following typical CHS geometry alignment) they start at the beginning of a cylinder.
::If a computer is booted with no partitions defined, and the first partition is created with the Vista installation disk, it will instead use the 1-MB alignment. (The partitioner on the Vista installation disk follows the 1-MB alignment just as Vista Disk Management does.) By following a 1-MB alignment, all partitions will have an even numbered offset (so long as no other partitioner is used on the drive).
*Using a 1-
MB alignment boundary allows safer editing of the partition table with Vista Disk Management.
:Partition tables using a CHS geometry (or some mix of alignments) may prevent Vista from resizing partitions or it may produce unconventional partition tables. For example, the endings of the "
EBR extended partitions" (type ) may overlap other partitions, and it will leave unprecedented amounts of space between an
extended boot record
An extended boot record (EBR), or extended partition boot record (EPBR), is a descriptor for a logical partition under the common DOS disk drive partitioning system. In that system, when one (and only one) partition record entry in the master boot ...
and its logical drive.
Ranish Partition Manager
Ranish Partition Manager is a freeware hard disk partition editor, disk cloning utility, and boot manager, that gives a high level of control for creating multi-boot systems. It is available on the freeware live CD SystemRescueCD and the Ultimat ...
does not show an error if there are more than 63 sectors between the EBR and its logical volume, ''so long as'' the
EBRs and
VBRs are on the ''first sector of any track (head)''. If either the VBR or the EBR are not on the first sector of a head,
Ranish Partition Manager
Ranish Partition Manager is a freeware hard disk partition editor, disk cloning utility, and boot manager, that gives a high level of control for creating multi-boot systems. It is available on the freeware live CD SystemRescueCD and the Ultimat ...
shows the "partition" in red and when the partition is highlighted, this error message appears: "Boot sector doesn't have valid information". Using the 1-MB alignment boundary will not put VBRs or EBRs on the first sector of a track (according to any standard CHS geometry) and Vista Disk Management will not use the CHS geometry of a partition table created with a different partition editor.
*A disk that is solely partitioned with Vista Disk Management can create partitions in exact MB sizes and never leave leftover bits of space between partitions. (As long as you don't count the full 1 MB allocated for each logical partition to contain just a single sector extended boot record.)
:With Vista DM, all the logical drives besides the one nearest the beginning of the extended partition (type
0x0F), usually reserve exactly one additional MB, for an
extended boot record
An extended boot record (EBR), or extended partition boot record (EPBR), is a descriptor for a logical partition under the common DOS disk drive partitioning system. In that system, when one (and only one) partition record entry in the master boot ...
, instead of the 63 sectors (31.5 KB) that is most commonly reserved according to alignments based on a CHS geometry. If other partition editors are used on the disk then Vista DM may reserve different amounts of space for the
EBRs.
See also
*
Logical volume management
In computer storage, logical volume management or LVM provides a method of allocating space on mass-storage devices that is more flexible than conventional partitioning schemes to store volumes. In particular, a volume manager can concatenate, ...
*
Storage virtualization
In computer science, storage virtualization is "the process of presenting a logical view of the physical storage resources to" a host computer system, "treating all storage media (hard disk, optical disk, tape, etc.) in the enterprise as a singl ...
*
Logical Volume Manager (Linux)
In Linux, Logical Volume Manager (LVM) is a device mapper framework that provides logical volume management for the Linux kernel. Most modern Linux distributions are LVM-aware to the point of being able to have their root file systems on a l ...
(LVM)
*
List of Microsoft Windows components
The following is a list of Microsoft Windows computer program, components.
Configuration and maintenance
User interface
Applications and utilities
Windows Server components
File systems
Core components
Services
This list i ...
*
diskpart
In computing, diskpart is a command-line disk partitioning utility included in Windows 2000 and later Microsoft operating systems, replacing its predecessor, fdisk. The command is also available in ReactOS.
Overview
The diskpart is a utility ...
References
External links
Captive-NTFS Logical Disk Manager FAQComparison matrix of Windows LDM and Veritas Volume Managerlibldm — LGPL library for reading Windows LDM on Linux
{{Windows Components
Windows components
Windows NT architecture
Volume manager