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FastTrak SX4030, SX4060, S150 SX4-M User Manual
About Dual Data Redundancy
One unique (though rarely occurring) feature of RAID 0+1 is dual fault tolerance.
In some cases, two drives can fail simultaneously and still maintain the integrity
of data. There are six combinations in which two drives can fail. The FastTrak
SX4030, SX4060 or S150 SX4-M card protects the data array in four of those
cases. Assume the drives are configured as follows:
•
CH indicates channels on the FastTrak Controller card.
•
A/B indicates which striped pair the drive belongs to.
•
1/2 indicates which part of stripe data.
Under RAID 0+1, the array maintains data integrity if any 1, 2 combination
survives.
Failed
Event
Dives
1
A1/A2
2
B1/B2
3
A1/B2
4
B1/A2
5
A1/B1
6
B2/A2
CH1
CH2
Drive A1
Drive A2
Array
Status
Functional
Functional
Functional
Functional
Offline
Offline
CH3
Drive B1
Drive B2
B1/B2 retain array integrity
A1/A2 retain array integrity
B1/A2 retain array integrity
A1/B2 retain array integrity
B2/A2 contain only half the array data
A1/B1 contain only half the array data
46
CH4
Why?
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