User`s manual

FastTrak100 TX/LP™ Series User Manual
82
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
TM
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.