Compaq RAID ARRAY 3000 EK-SMCPO-UG. C01 - Manual (Page 43)

RAID Array Controller 2-9
Compaq Confidential – Need to Know Required
Writer: Bob Young Project: RAID Array 3000 Pedestal Storage Subsystem Hardware User’s Guide Comments:
Part Number: EK-SMCPO-UG. C01 File Name: c-ch2 RAID Array Controller.doc Last Saved On: 12/4/00 1:51 PM
■ Each RAID set can be partitioned into smaller redundancy groups.
■ The controller’s host LUN Mapping feature makes it possible to map
RAID sets differently to each host port. You make the same redundancy
group appear on different LUNs to different hosts, or make a
redundancy group visible to one host but not to another.
■ Any drive may be designated as a hot or warm spare. Spares are global,
meaning that in the event of a drive failure, the controller will search for
the first available spare on any channel or SCSI ID and automatically
begin rebuilding the failed drive’s data.
Performance Enhancements
The controller employs a number of techniques to achieve as much
performance as possible from its design.
Custom Components
To increase performance and reliability, the controller’s core functions have
been encapsulated in four custom Application Specific Integrated Circuits
(ASIC) components as follows:
■ XOR ASIC: Used in the exclusive -or parity calculations employed by
RAID levels 4 and 5.
■ DMA ASIC: Controls the data path hardware for the various I/O ports
■ CPU Interface ASIC: Supports the controller’s MIPS R3000 RISC
central processing unit.
■ Memory Controller ASIC: Controls the memory system and supports
data movement on the internal bus at a maximum burst rate of 80 Mb/s
and a maximum sustainable rate of 60 Mb/s.