User`s guide

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4: Using the RAID Controller
The disk drive modules are dual-ported. A RAID controller sees 16 to 32 drives on each
loop (A and B), because it finds both ports of each drive. Via the I/O modules, it
alternates allocation of the drives between channels, so that the drive addresses are
available for failover. At startup, half the drives are on channel 0 via their A port and the
other half are on channel 1 via their B port; each I/O module controls a separate loop of
half the drives. Figure 4-2 diagrams this arrangement for the tower.
Figure 4-2 Tower I/O Modules, Channels, and Loops
Figure 4-3 diagrams disk addressing for a rackmount RAID system with a full
complement of disks in three enclosures.
Channel 0
Channel 1
Channel 1
Channel 0
Channel 1
Channel 0
First I/O module, FC drive loop A (channel 0)
target 7
target 11
target 15
target 6
target 10
target 14
Channel 0
Channel 1 Channel 1
Channel 0
Channel 1
Channel 0
target 5
target 9
target 13
target 4target 8 target 12
loop ID 12 loop ID 4
loop ID 5
loop ID 6
loop ID 7
loop ID 8
loop ID 9
loop ID 10
loop ID 11
l oop ID 13
loop ID 14
loop ID 15
Channel 0
target 19
Channel 0
Channel 1
target 17
target 16
loop ID 16
loop ID 17
loop ID 19
Channel 1
target 18
loop ID 18
Second I/O module, FC drive loop B (channel 1)