Promise Technology FAST TRAK100TM - Manual (Page 72)

FastTrak100 User Manual
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Mirroring (RAID 1)
Writes duplicate data on to a pair of drives while reads are performed in parallel.
ATA RAID 1 is fault tolerant because each drive of a mirrored pair is installed on
separate IDE channels. If one of the mirrored drives suffers a mechanical failure
(e.g. spindle failure) or does not respond, the remaining drive will continue to
function. This is called Fault Tolerance. If one drive has a physical sector error,
the mirrored drive will continue to function.
RAID 1 (Mirroring)
On the next reboot, the FastBuild T M utility will display an error in the array and
recommend to replace the failed drive. Users may choose to continue using their
PC, however Promise recommends replacing the failed drive as soon as possible.
See Chapter 4 for a functional description.
Due to redundancy, the drive capacity of the array is half the total drive capacity.
For example, two 1GB drives that have a combined capacity of 2GB would have
1GB of usable storage. With drives of different capacities, there may be unused
capacity on the larger drive.
Using a Spare Drive
Under a RAID 1 setup, an extra “hot spare” drive (a third drive on FastTrak100)
can be attached to the FastTrak100 and not assigned to the array. Such a drive will
be activated to replace a failed drive that is part of a mirrored array. A rebuild is
performed automatically in the background to mirror the good drive data on to the
spare.
At a later time, the system can be powered off and the failed drive can be
physically removed and replaced. Spare drives must be the same or larger capacity
than the smallest array member.