Vinum, is a logical volume manager

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...

, also called Software RAID, allowing implementations of the RAID-0, RAID-1 and RAID-5 models, both individually and in combination. Vinum is part of the base distribution of the FreeBSD

FreeBSD

FreeBSD is a free Unix-like operating system descended from AT&T UNIX via BSD UNIX. Although for legal reasons FreeBSD cannot be called “UNIX”, as the direct descendant of BSD UNIX , FreeBSD’s internals and system APIs are UNIX-compliant...

 operating system. Versions exist for NetBSD

NetBSD

NetBSD is a freely available open source version of the Berkeley Software Distribution Unix operating system. It was the second open source BSD descendant to be formally released, after 386BSD, and continues to be actively developed. The NetBSD project is primarily focused on high quality design,...

, OpenBSD

OpenBSD

OpenBSD is a Unix-like computer operating system descended from Berkeley Software Distribution , a Unix derivative developed at the University of California, Berkeley. It was forked from NetBSD by project leader Theo de Raadt in late 1995...

 and DragonFly BSD

DragonFly BSD

DragonFly BSD is a free Unix-like operating system created as a fork of FreeBSD 4.8. Matthew Dillon, an Amiga developer in the late 1980s and early 1990s and a FreeBSD developer between 1994 and 2003, began work on DragonFly BSD in June 2003 and announced it on the FreeBSD mailing lists on July...

. Vinum source code

Source code

In computer science, source code is text written using the format and syntax of the programming language that it is being written in. Such a language is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source...

 is currently maintained in the FreeBSD source tree. Vinum supports raid levels 0, 1, 5, and JBOD. Vinum is invoked as gvinum (GEOM

GEOM

GEOM is the main storage framework for the FreeBSD operating system. It is available in FreeBSD 5.0 and higher and provides a standardized way to access storage layers. GEOM is modular and allows for geom modules to connect to the framework. For example, the geom_mirror module will provide RAID1 or...

 Vinum) on FreeBSD version 5.4 and up.

Software RAID vs. Hardware RAID

The distribution of data across multiple disks can be managed by either dedicated hardware or by software. Additionally, there are hybrid RAIDs that are partly software- and partly hardware-based solutions.

With a software implementation, the operating system manages the disks of the array through the normal drive controller (ATA

AT Attachment

Parallel ATA , originally ATA, is an interface standard for the connection of storage devices such as hard disks, solid-state drives, floppy drives, and optical disc drives in computers. The standard is maintained by X3/INCITS committee...

, SATA

Sata

Sata is a traditional dish from the Malaysian state of Terengganu, consisting of spiced fish meat wrapped in banana leaves and cooked on a grill.It is a type of Malaysian fish cake, or otak-otak...

, SCSI

SCSI

Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it...

, Fibre Channel

Fibre Channel

Fibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the T11 Technical Committee of the InterNational Committee for Information Technology Standards , an American National Standards Institute –accredited standards...

, etc.). With present CPU speeds, software RAID can be faster than hardware RAID.

A hardware implementation of RAID requires at a minimum a special-purpose RAID controller. On a desktop system, this may be a PCI

Peripheral Component Interconnect

Conventional PCI is a computer bus for attaching hardware devices in a computer...

 expansion card, or might be a capability built in to the motherboard. In larger RAIDs, the controller and disks are usually housed in an external multi-bay enclosure. This controller handles the management of the disks, and performs parity calculations (needed for many RAID levels). This option tends to provide better performance, and makes operating system support easier.

Hardware implementations also typically support hot swapping, allowing failed drives to be replaced while the system is running. In rare cases hardware controllers have become faulty, which can result in data loss. Hybrid RAIDs have become very popular with the introduction of inexpensive hardware RAID controllers. The hardware is a normal disk controller that has no RAID features, but there is a boot-time application that allows users to set up RAIDs that are controlled via the BIOS

BIOS

In IBM PC compatible computers, the basic input/output system , also known as the System BIOS or ROM BIOS , is a de facto standard defining a firmware interface....

. When any modern operating system is used, it will need specialized RAID drivers that will make the array look like a single block device. Since these controllers actually do all calculations in software, not hardware, they are often called "fakeraids". Unlike software RAID, these "fakeraids" typically cannot span multiple controllers.

Example configuration

A simple example to mirror drive enterprise to drive excelsior (RAID1)

drive enterprise device /dev/da1s1d

drive excelsior device /dev/da2s1d

volume mirror

  plex org concat

    sd length 512m drive enterprise

  plex org concat

    sd length 512m drive excelsior

See also

• Hard drives
• Redundant array of independent disks
• Disk array
  Disk array
  A disk array is a disk storage system which contains multiple disk drives. It is differentiated from a disk enclosure, in that an array has cache memory and advanced functionality, like RAID and virtualization.Components of a typical disk array include:...
  
  
• Storage area network
  Storage area network
  A storage area network is a dedicated network that provides access to consolidated, block level data storage. SANs are primarily used to make storage devices, such as disk arrays, tape libraries, and optical jukeboxes, accessible to servers so that the devices appear like locally attached devices...
  
  (SAN)

External links

• Vinum page in the official FreeBSD handbook
• Sourceforge page
• Bootstrapping vinum - FreeBSD documentation project
• Vinum performance measurement