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For example, if three drives are arranged in RAID 3, this gives an array space efficiency of 1 − 1/n = 1 − 1/3 = 2/3 ≈ 67%; thus, if each drive in this example has a capacity of 250 GB, then the array has a total capacity of 750 GB but the capacity that is usable for data storage is only 500 GB.
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.
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.
It is up to controllers to provide advanced functionality (various vendors name these differently): Automatic failover to another controller (transparent to computers transmitting data) Long-running operations performed without downtime. Forming a new RAID set; Reconstructing degraded RAID set (after a disk failure) Adding a disk to online RAID set
The AX150 supports up to 12 Serial ATA disks with either 250, 500 or 750 GB (1 GB = 10 9 B) at a throughput of 150 (250 GB disks) or 300 MB/s (500, 750 GB disks) and, optionally, NCQ. Supported RAID levels are RAID 5 (with min. 3 disks) and RAID 1/0 (min. 4 disks).
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In a non-RAID application, it may be important for a disk drive to go to great lengths to successfully read a problematic storage block, even if it takes several seconds. In an appropriately configured RAID array, a single bad block on a single drive can be recovered completely via the redundancy encoded across the RAID set.
Linux supports Matrix RAID and Rapid Storage Technology (RST) through device mapper, with dmraid tool, for RAID 0, 1 and 10. And Linux MD RAID, with mdadm tool, for RAID 0, 1, 10, and 5. Set up of the RAID volumes must be done by using the ROM option in the Matrix Storage Manager, then further configuration can be done in DM-RAID or MD-RAID. [10]