2
RAID Array Controller
This chapter describes the major features and characteristics of the RAID array control- ler in the controller shelf.
2.1Controller Overview
The RAID Array controller provides high performance, high-availability access to SCSI disk array subsystems along a wide UltraSCSI bus. With a modular hardware design and an intuitive configuration utility, the controller is designed to meet a wide range of storage needs.
The controller consists of a single 5 1/2” x 8” circuit board mounted in a subas- sembly. The package consists of the controller board, a 300-pin connector, me- chanical insertion assists, and a front panel LED/reset switch interface. All sig- nals to the controller are routed through the backplane connector.
Figure 2–1 shows a simplified block diagram of the controller and its interfaces to the major components in the RAID Array 3000 . The unit is configured with two Ultra-Wide, differential, SCSI host channels capable of transferring data to and from the host at rates up to 40 MB/s. The host SCSI IDs are configurable via the Host Parameters and can support 32 deep tagged queuing. The controller is also configured with two Ultra-Wide, single-ended, SCSI disk channels capable of transferring data to and from the disk drives at rates up to 40 MB/s. Each channel can support up to 12 drives.
The controller has two SIMM connectors. The connectors form a mirrored pair when the controllers are configured in a redundant controller configuration; oth- erwise they are fully accessible by the controller. In a redundant controller setup, both controllers must have identical cache configurations and the total usable cache (per controller) will be half the amount installed. Thus, in a single con- troller setup the maximum usable cache is 128 MB while a redundant setup has a maximum usable cache of 64 MB (per controller).