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Diagram of a RAID 1 setup. RAID 1 consists of an exact copy (or mirror) of a set of data on two or more disks; a classic RAID 1 mirrored pair contains two disks.This configuration offers no parity, striping, or spanning of disk space across multiple disks, since the data is mirrored on all disks belonging to the array, and the array can only be as big as the smallest member disk.
The different schemes, or data distribution layouts, are named by the word "RAID" followed by a number, for example RAID 0 or RAID 1. Each scheme, or RAID level, provides a different balance among the key goals: reliability , availability , performance , and capacity .
RAID 01, also called RAID 0+1, is a RAID level using a mirror of stripes, achieving both replication and sharing of data between disks. [3] The usable capacity of a RAID 01 array is the same as in a RAID 1 array made of the same drives, in which one half of the drives is used to mirror the other half.
With a software implementation, the operating system manages the disks of the array through the normal drive controller (ATA, SATA, SCSI, Fibre Channel, 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.
The four-drive example is identical to a standard RAID 1+0 array, while the three-drive example is a software implementation of RAID 1E. The two-drive example is equivalent to RAID 1. [13] The driver also supports a "far" layout, in which all the drives are divided into f sections. All the chunks are repeated in each section but are switched in ...
RAIS stripes and mirrors application code and memory across an array of ordinary servers using the standard RAID schemata of level 0, level 1, level 5, level 1+0. This is possible through a memory management system called Versioned Memory. [citation needed] Data blocks of each stream are striped across the array servers.
In some RAID configurations, such as RAID 0, failure of a single member drive of the RAID array causes all stored data to be lost. In other RAID configurations, such as a RAID 5 that contains distributed parity and provides redundancy , if one member drive fails the data can be restored using the other drives in the array.
It often implements hardware RAID, thus it is sometimes referred to as RAID controller. It also often provides additional disk cache . Disk array controller is often ambiguously shortened to disk controller which can also refer to the circuitry responsible for managing internal disk drive operations.