Promise Technology FastTrak TX2000 User Manual page 51

installed. With a four-drive disk array, two pairs of drives are striped. Each pair mirrors the data
on the other pair of striped drives. The data capacity is similar to a standard Mirroring array with
half of total capacity dedicated for redundancy.
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. FastTrak TX2000 protects the data array in four of
those cases depending on drive type (some drives do not permit the Slave drive to continue to
function if the Master drive fails).
Assume the drives are configured as follows (M = Master, A/B indicates which striped pair the
drive belongs to, # indicates which part of stripe data):
FastTrak TX2000™ Series User Manual
IDE 1
M
Drive A1
S Drive B2
IDE2
Drive B1
Drive A2
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