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RM16_EX8
User
Guide
v1.0
‐
DATOptic.com
drive for data protection. RAID 10 has been traditionally implemented
using an even number of disks, some hybrids can use an
odd number of disks as well. Illustration is an example of a hybrid
RAID 10(1E) array comprised of five disks; A, B, C, D and E.
In this configuration, each strip is mirrored on an adjacent disk
with wrap-around. Areca RAID 10 offers a little more flexibility in
choosing the number of disks that can be used to constitute an
array. The number can be even or odd.
•
RAID 3
RAID 3 provides disk striping and complete data redundancy
though a dedicated parity drive. RAID 3 breaks up data into
smaller blocks, calculates parity by performing an exclusive-or
on the blocks, and then writes the blocks to all but one drive in
the array. The parity data created during the exclusive-or is then
written to the last drive in the array. If a single drive fails, data is
still available by computing the exclusive-or of the contents corresponding
strips of the surviving member disk. RAID 3 is best
for applications that require very fast data- transfer rates or long
data blocks.
APPENDIX
168
•
RAID 5
RAID 5 is sometimes called striping with parity at byte level. In
RAID 5, the parity information is written to all of the drives in the
controllers rather than being concentrated on a dedicated parity
disk. If one drive in the system fails, the parity information can
be used to reconstruct the data from that drive. All drives in the
array system can be used for seek operations at the same time,
greatly increasing the performance of the RAID system. This
relieves the write bottleneck that characterizes RAID 4, and is the
primary reason that RAID 5 is more often implemented in RAID
arrays.
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APPENDIX
Summary of RAID Levels
The RM16_EX8 raid engine supports RAID Level 0, 1, 10(1E), 3, 5 and
6. The table below provides a summary of RAID levels.
Features and Performance
RAID
Level
Description Min.
Drives
Data
Reliability
Data
Transfer
Rate
I/O Request
Rates
0 Also known as stripping
Data distributed across multiple
drives in the array. There is no
data protection.
1 No data
