INTRODUCTION
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1.7.6 RAID 6
RAID 6 provides the highest reliability, but is not yet widely used.
It is similar to RAID 5, but it performs two different parity com-
putations or the same computation on overlapping subsets of
the data. RAID 6 can offer fault tolerance greater than RAID 1 or
RAID 5 but only consumes the capacity of 2 disk drives for dis-
tributed parity data. RAID 6 is an extension of RAID 5 but uses a
second, independent distributed parity scheme. Data is striped on
a block level across a set of drives, and then a second set of par-
ity is calculated and written across all of the drives.
Summary of RAID Levels
The SATA RAID controller supports RAID Levels 0, 1, 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
Protection
Very High Very High for
Both Reads and Writes
1 Also known as mirroring
All data replicated on N separated disks.
N is almost always 2.
This is a high availability solution, but due
to the 100% duplication, it is also a costly
solution. Half of drive capacity in array
devoted to mirroring.
2 Lower
than RAID
6;
Higher
than
RAID 3, 5
Reads are
higher
than a
single disk;
Writes
similar to a
single disk
Reads are twice as fast
as a single disk;
Write are similar to a
single disk.
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