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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.
Those RAID systems made their way to the consumer market, for users wanting the fault-tolerance of RAID without investing in expensive SCSI drives. Fast consumer drives make it possible to build RAID systems at lower cost than with SCSI, but most ATA RAID controllers lack a dedicated buffer or high-performance XOR hardware for parity calculation.
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.
RAID (/ r eɪ d /; redundant array of inexpensive disks or redundant array of independent disks) [1] [2] is a data storage virtualization technology that combines multiple physical data storage components into one or more logical units for the purposes of data redundancy, performance improvement, or both.
A parity drive is a hard drive used in a RAID array to provide fault tolerance. For example, RAID 3 uses a parity drive to create a system that is both fault tolerant and, because of data striping, fast. [1] Basically, a single data bit is added to the end of a data block to ensure the number of bits in the message is either odd or even. [2]
A RAID level is any of the possible configurations of a RAID disk array. RAID stands for redundant array of independent disks (or, formerly, redundant array of inexpensive disks ). RAID levels may refer to:
The hot spare disk reduces the mean time to recovery (MTTR) for the RAID redundancy group, thus reducing the probability of a second disk failure and the resultant data loss that would occur in any singly redundant RAID (e.g., RAID-1, RAID-5, RAID-10). Typically, a hot spare is available to replace a number of different disks and systems ...
A flawed RAID 5/6 also exists, but can result in data loss.) [10] For RAID 1, the devices must have complementary sizes. For example, a filesystem spanning two 500 GB devices and one 1 TB device could provide RAID1 for all data, while a filesystem spanning a 1 TB device and a single 500 GB device could only provide RAID1 for 500 GB of data.