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THOR's Architectural Configurations

Data Processing Nodes

In Hitachi's THOR MPP Data Server™ architecture, the basic building block is a Data Processing Node, simply referred to as a node. In the THOR system, a node is a complete RISC-based computer system equipped with a processor and I/O subsystem that interconnects to other such nodes. The processors and adapters are all connected via a local PCI bus, and all are packaged together within a compact field-replaceable unit.

As noted earlier, the components have been selected to provide the maximum price/performance, with high volume, off-the-shelf parts used wherever possible. The system is designed to function in a normal office operating environment.

The configuration within each processor node is shown schematically in Figure 6.

Figure 6. Processor node schematic

Two kinds of nodes

There are two kinds of processor nodes, distinguished mainly by the software present on them. Interface processor nodes (IPNs) connect THOR to the outside world through a high-speed channel attachment. Database processor nodes (DPNs) are repositories for the data and contain database query execution software.

Unlike some other systems, THOR IPNs may also act concurrently as DPNs. Figure 7 illustrates a schematic of a possible IPN and DPN configuration.

Figure 7. Schematic view of THOR's IPN and DPN configuration

The node's communication processor

As indicated earlier, the dedicated communications processor connects the node to the toroidal mesh backbone network. The communications processor has DMA access to the memory and supports four simultaneous bi-directional links, for a total sustained bandwidth of 64 Megabytes per node per second. The processor also functions as a router to significantly offload the main processor.

Modules

Four nodes = one module

Up to four nodes are packaged together into a module, which contains cabling attachments and N+1 redundant power supplies. The module is the smallest stand-alone unit of a THOR system; any THOR system must have enough module enclosures to contain all of its nodes. A module supports a sustained bandwidth of 256 Megabytes/second.

The database system and the operating system operate together to distribute user data, manage each node's devices, process queries, and provide communications. This means that all the components in the module operate at near linear scaleability as the nodes balance the workload for data processing. To increase the processing power, simply add more modules to the system and the workload capacity processing power will increase proportionally.

Towers

One to six modules = one tower

As shown in Figure 8, modules may be stacked into "towers" up to six modules high, and towers may be interconnected to expand a THOR system still further. A tower with six modules supports a sustained bandwidth of 1.5 Gigabytes/second. Although there is no architectural limit to the number of towers, the present hardware system has been designed to support up to twelve interconnected towers for a total of 288 nodes.

Figure 8. Data Processing Nodes, Modules and Towers

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