HP StorageWorks 3000 RAID Array - Manual (Page 45)

RAID Array 3000 Controller 2-3
Compaq Confidential – Need to Know Required
Writer: Bob Young Project: RAID Array 3000 Controller Shelf Hardware User’s Guide Comments:
Part Number: EK-SMCPQ-UG. D01 File Name: c-ch2 RAID Array 3000 Controller.doc Last Saved On: 12/4/00 1:08 PM
There are two configurations for redundant pairs of controllers: active/active
failover mode and active/passive failover mode. In active/active failover, each
controller in the redundant pair has one active SCSI host port and one passive
SCSI host port. Redundancy groups (virtual LUNS) can be mapped to only
one active host port and are not accessible from the passive port or the other
controller (that is, partitioned model).
In active/passive failover, one controller in the redundant pair has both SCSI
host ports active and the other controller is in a standby passive mode.
redundancy groups (virtual LUNs) can be mapped to either SCSI host port or
to both as in the single controller model.
In both cases a single controller failure will not affect the subsystem because
the surviving controller will take over.
Controller Features
The controller is the intelligent bridge between the host and the devices in the
shelf. From the host’s perspective, the controller is simply another SCSI
device connected to one of its I/O buses. Consequently, the host sends its I/O
requests to the controller just as it would to any other SCSI device. Figure 2– 2
shows the role of the controller between the host and the device expansion
shelf.
SHR-1042
Storage
Shelf
Controller
Host
Figure 2-2. Bridging the gap between the host and device expansion shelf