Promise Technology FASTtrak100 TX User Manual page 87

NOTE: Due to IDE limitations when drives are in a Master/Slave configuration, if the
drive that fails is on the same channel as the "spare" drive, there is a possibility that
the "spare" drive will fail to be recognize d by the system. For this reason Promise
recommends using "spare" drives only on the FastTrak100 TX4.
Striping/Mirror (RAID 0+1)
A combination of both above array types. It can increase performance by reading
and writing data in parallel while protecting data with duplication. A minimum of four
drives needs to be 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. FastTrak100 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):
FastTrak100 TX/LP™ Series User Manual
IDE 1
M
Drive A1
IDE2
Drive B1
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