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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.
As such, a Matrix RAID array can improve both performance and data integrity. A practical instance of this would use a small RAID 0 (stripe) volume for the operating system, program, and paging files; second larger RAID 1 (mirror) volume would store critical data. Linux MD RAID is also capable of this. [7] [8] [9]
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.
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.
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]
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.
Replication is enabled via microcode on the disk array controller or via server software. It is typically a proprietary solution, not compatible between various data storage device vendors. Mirroring is typically only synchronous. Synchronous writing typically achieves a recovery point objective (RPO) of zero lost data. Asynchronous replication ...
While hardware RAID controllers have been available for a long time, they initially required expensive Parallel SCSI hard drives and aimed at the server and high-end computing market. SCSI technology advantages include allowing up to 15 devices on one bus, independent data transfers, hot-swapping , much higher MTBF .