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Chapter 11. Performance considerations 221
Figure 11-1 Host server and storage server comparison: Balanced throughput challenge
The challenge is obvious: Develop a storage server—from the top with its host adapters down
to its disk drives—that creates a balanced system with respect to each component within this
storage server and with respect to their interconnectivity with each other. All this must be
done while taking into consideration other requirements as well, like investment protection
and being competitive not only in performance but also with respect to price and reliability.
A further requirement is to keep the life cycle of the product as long as possible due to the
substantial development costs for an all new product. Furthermore, provide a storage family
approach with a single management interface and the potential to adopt new technology as it
develops on a component level. The simple picture suggests that this a more difficult task for
a storage server than for a host server. Perhaps it became this way with the evolving
complexity of storage servers.
11.2 Where do we start?
The IBM Enterprise Storage Server 2105 (ESS) already combined everything mentioned in
the previous paragraph when it appeared in the marketplace in 1999. Over time the ESS
evolved in many respects to enhance performance and to improve throughput. Despite the
powerful design, the technology and implementation used eventually reached its life cycle
end.
Looking more closely at the components in the ESS and their enhancements from the E20 to
the F20 to the 800 and 800 Turbo II models, some components reached their architectural
limits at various levels. This section briefly reviews the most obvious limitations that were
encountered over time as the other components were enhanced. It has to be noted that the
ESS 800 is still a very competitive disk storage server which outperforms other storage
servers in many respects.
Processor
Adapter
Adapter
Memory
Memory
Processor
Processor
Adapter
Adapter
Memory
Memory
Processor
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Adapter
To host servers
To storage servers
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Storage server