Addonics Technologies Users Guide v1.0
2-Port SATA II RAID5/JBOD PCI Express Controller Card
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Chapter 2
RAID tutorial
2. What is RAID?
RAID - Redundant Array of Independent Disks
RAID technology manages multiple disk drives to enhance I/O performance
and provide redundancy in order to withstand the failure of any
individual member, without loss of data. This card provides two RAID Set
types, Striped (RAID 0) and Mirrored (RAID 1).
2.1 Disk Striping (RAID 0)
Striping is a performance-oriented, non-redundant data mapping technique.
While Striping is discussed as a RAID Set type, it is actually does not provide
fault tolerance. With modern SATA bus mastering technology, multiple
I/O operations can be done in parallel, enhancing performance. Striping
arrays use multiple disks to form a larger virtual disk.
2.2 Disk Mirroring (RAID 1)
Disk mirroring creates an identical twin for a selected disk by having the data
simultaneously written to two disks. This redundancy provides instantaneous
protection from a single disk failure. If a read failure occurs on one drive, the
system reads the data from the other drive.
2.3 Mirrored-Striping (RAID 1+0)
A Mirrored-Striping Set does just what it says, combining both Striping and
Mirroring technologies to provide both the performance enhancements that
come from Striping and the data availability and integrity that comes
from Mirroring. When data is written to a Mirrored-Striped Set, instead of
creating just one virtual disk, as Striping would do, a second, mirrored virtual
disk is created as well.
2.4 Parity RAID (RAID 5)
Parity or RAID 5 adds fault tolerance to Disk Striping by including parity
information with the data. Parity RAID dedicates the equivalent of one disk
for storing parity stripes. The data and parity information is arranged on the
disk array so that the parity is written to different disk. There are at least 3
members to a Parity RAID set.
2.5 JBOD (Just Bunch of Disks)
The JBOD is a virtual disk that can either be an entir e disk drive or a segment
of a single disk drive.
