IBM 86655RY - Netfinity 7600 - 8665 Hardware Maintenance Manual page 206

With RAID level-1, if one of the physical drives fails, the ServeRAID controller
switches read and write requests to the remaining functional drive in the RAID level-
1 array.
Understanding RAID level-1 Enhanced: If you have three or more physical drives in
the array, you cannot select RAID level-1; you can select RAID level-1 Enhanced
(RAID level-1E).
RAID level-1E combines mirroring with data striping. This RAID level stripes data
and copies of the data across all of the drives in the array. As with the standard RAID
level-1, the data is mirrored, and the capacity of the logical drive is 50 percent of the
array capacity of the grouping of physical drives in the array.
RAID level-1E requires a minimum of 3 drives and supports a maximum of 16 drives.
The following illustration is an example of a RAID level-1E logical drive.
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Hardware Maintenance Manual: Netfinity 7600 – Type 8665 Models 1RY, 2RY
Notice that the data on the drive on the right is a copy of the drive on the
left.
Start with three physical drives.
Create an array using the physical drives.
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1
2 2
3
3
4 4