Volume (computing) |
== Introduction and Definition ==
In the context of computer operating systems (including Windows 2000 and XP), where they are handled by the kernel and managed using the Disk Manager MMC snap-in.
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== Differences between Volume and Partition ==
A volume is not the same thing as a partition. For example, a floppy disk might be accessible as a volume, even though it does not contain a partition, as floppy disks cannot be partitioned with most modern computer hardware. Also, an OS can recognize a parition without recognizing any volume associated with it, as when the OS cannot interpret the filesystem stored there. This situation occurs, for example, with Windows NT-based OSes and most non-Microsoft OS partitions, such as with the EXT3 filesystem commonly used with Linux.
== Example ==
This example concerns a Windows XP system with two physical hard disks. The first hard disk has two partitions, the second has only one. The first partition of the first hard disk contains the operating system. Mount points have been left at defaults.
In this example,
= Nomenclature of volumes =
=== Windows-NT based operating systems ===
It is important to note that Windows NT-based OSes do not have a single root directory. As a result, Windows will assign at least one path to each mounted volume, which will take one of two forms:
In these two examples, a file called Track 1.mp3 stored in the root directory of the mounted volume could be referred to as F:Track 1.mp3 or C:MusicTrack 1.mp3 respectively.
In order to assign a mount point for a volume as a path within another volume, the following criteria must be met:
By default, Windows will assign drive letters to all drives, as follows:
Because of this convention, the operating system startup drive is most commonly called C: . This is not always the case.
On Windows XP, mount points may be managed through the Disk Management snap-in for the Microsoft Management Console. This can be most conveniently accessed through Computer Management in the Administrative Tools section of the Control Panel.
More than one drive letter can reffer to a single volume, as when using the command.
Warning: removing drive letters or mount-points for a drive may break some programs, as some files may not be accessible under the known path. For example, if a program is installed at D:Program FilesSome Program , it may expect to find it s data files at D:Program FilesSome ProgramData . If the logical disk previously called D: has it s drive letter changed to E: , Some Program won t be able to find it s data at D:Program FilesSome ProgramData , since the drive letter D: no longer represents that volume.
== Unix-like Operating Systems ==
In Unix-like operating systems, volumes other than the boot volume have a mount-point somewhere with the filesystem, represented by a path. Logically, the directory tree stored on the volume is grafted in at the mountpoint. By convention, mount-points will often be placed in a directory called /mnt , though /media and other terms are sometimes used.
Like in Windows, to use a given path as a mount-point for another volume, an empty directory (sometimes called a folder) must exist there.
Unix-like operating systems use the mount command to manipulate mount points for volumes.
For example, if a CD-ROM drive containg a text file called info.txt was mounted at /mnt/iso9660 , the text file would be accessible at /mnt/iso9660/info.txt .
== Benefits of keeping files within a single volume ==
== Speed of data management ==
Files within a volume can generally be moved to any other place within that volume by manipulating the filesystem, without moving the actual data. However, if a file is to be moved outside the volume, the data itself must be relocated, which is a much more intensive operation.
In order to better visualize this concept, one might consider the example of a large library. If a non-fiction work is origionally classified as having the subject plants , but then has to be moved to the subject flora , one does not need to refile the book, who s position on the shelf would be static, but rather, one needs only to replace the index card. However, to move the book to another library, adjusting index cards alone is insufficient. The entire book must be moved.
=== Special functions of advanced filesystems and volumes ===
Some filesystems, such as Microsoft s proprietary (UNIX & variants), which can refer to files on another volume in some cases. FAT filesystems, such as FAT-32, do not support hard or soft links as such, although the Windows operating system supports links , which are somewhat less capable.
== See Also ==
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