Compaq External RAID Controller & Subsystem Infortrend Operation Manual page 29

In the example shown below, the member of Logical Drive 0 are 9
GB drives, and the members in Logical Drives 1 and 2 are 4 GB
drives.
Figure 1 - 12 Mixing Local and Global Spares
Local Spare Drive
LS
(9GB)
1 2
1
(9GB) (9GB) (4GB)
3
(9GB)
Logical Drive 0 Logical Drive 1
A Local Spare always has
higher priority than a
Global Spare.
Infortrend
Global Spare Drive
GS
(4GB)
1 2
2
(4GB) (4GB)
(4GB)
4 3
(4GB) (4GB)
Logical Drive 2
It is not possible for the 4 GB Global
Spare Drive to join Logical Drive 0
because of its insufficient capacity.
However, using a 9GB drive as the
Global Spare drive for a failed drive that
comes from Logical Drive 1 or 2 will
bring huge amount of excess capacity
since these logical drives require 4 GB
only. In the diagram below, the 9 GB
Local Spare Drive will aid Logical Drive
0 once a drive in this logical drive fails. If
the failed drive is in Logical Drive 1 or 2,
the 4 GB Global Spare drive will
immediately give aid to the failed drive.
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