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260 DS8000 Series: Concepts and Architecture
12.3.2 Fibre Channel device adapter
The DS8000 still relies on eight DDMs to form a RAID-5 or a RAID-10 array. These DDMs are
actually spread over two Fibre Channel loops and follow the successful approach to use AAL.
With the virtualization approach and the concept of extents, the DAs are mapping the
virtualization level over the disk subsystem back end. For more details on the disk subsystem
virtualization refer to Chapter 5, “Virtualization concepts” on page 83.
Figure 12-4 Fibre Channel device adapter with 2 Gbps ports
The new RAID device adapter is built on PowerPC technology with four 2 Gbps Fibre Channel
ports and high function, high performance ASICs. Each port provides up to five times the
throughput of a previous SSA-based DA port. Each single Fibre Channel protocol processor
satisfies both Fibre Channel 2 Gbps ports at full speed.
Note that each DA performs the RAID logic and frees up the processors from this task. The
actual throughput and performance of a DA is not only determined by the 2 Gbps ports and
hardware used, but also by the firmware efficiency.
12.3.3 New four-port host adapters
Before looking into the heart of the DS8000 series, we briefly review the new host adapters
and their enhancements to address performance. Figure 12-5 on page 261 depicts the new
host adapters. These adapters are designed to hold four Fibre Channel ports, which can be
configured to support either FCP or FICON. They are also enhanced in their configuration
flexibility and provide more logical paths, from 256 with an ESS FICON port to 2,048 per
FICON port on the DS8000 series.
Each port continues the tradition of providing industry-leading throughput and I/O rates for
FICON and FCP.
Note that a FICON channel can address up to 16,384 devices through a FICON port. The
DS8000 series can hold up to 65,280 devices and you need at least four additional FICON
channel ports to reach all potential volumes within a DS8000 disk storage server. With four
Processor
Adapter
Adapter
Adapter
Adapter
To host servers
Storage server
Memory
PowerPC
2 Gbps Fibre Channel ports
Fibre Channel
Protocol Proc
Fibre Channel
Protocol Proc
DA
Processor