USB 3.0-to-SATA II RAID Subsystem
User’s Manual
11
1.3 RAID Concepts
The basic idea of RAID (Redundant Array of Independent Disks) is to combine multiple
inexpensive disk drives into an array of disk drives to obtain performance, capacity and
reliability that exceeds that of a single large drive. The array of drives appears to the host
computer as a single logical drive.
The RAID subsystem provides data striping, mirroring, XOR calculation and data verification.
It supports RAID levels 0, 1, 3, 5, 10, LARGE and CLONE. All RAID levels’ capacity can
exceed 2 Terabytes. The RAID subsystem behaves as a full 48-bit addressing RAID drive
and is 100% ATA compliance.
From (PC) host controller, each logical device (RAID volume) controlled by the RAID system
acts just the same as single regular hard disk although a RAID system generally consists of
more than one hard disk drives. Therefore, no extra BIOS, driver or software is needed.
1.3.1 Definition of RAID Levels
Striping (RAID 0) for High Performance
Striping or RAID 0
is the segmentation of logically sequential
data, such as a single file, so that segment can be assigned to
multiple hard disks in a round-robin fashion and thus written
concurrently.
Advantage of RAID 0 is to achieve high performance by
accumulating each individual hard disk performance. However, if
any one hard disk gets defective, information stored in this RAID
0 will become invalid.
The RAID subsystem will just make use of the same disk space
for each hard disk under RAID 0 condition. For example, if a
RAID 0 consists of 5 different size hard disks, the total usable
space of this RAID 0 will be [capacity of smallest size hard disk] *
[the number of hard disks in this RAID 0].
Mirror (RAID 1) for High Security
Mirror or RAID1 is the replication of data onto separate hard disk
in real time to ensure continuous availability. In a RAID 1 system
with two hard disks, the data in one hard disk will be exactly the
same as the data in the other hard disk.
The RAID subsystem will also make use of same size disk space in
each hard disk in RAID 1. That is, the RAID controller will write
data to the same disk space in each hard disk. When reading data,
the RAID controller will read data from a specified hard disk.
