relatively small logical volumes, we ran out of device numbers to address an entire LSS. This happens even earlier when configuring not only real devices (3390B) within an LSS, but also alias devices (3390A) within an LSS in z/OS environments. By the way, an LSS is congruent to an logical control unit (LCU) in this context. An LCU is only relevant in z/OS and the term is not used for open systems operating systems.
11.3 How does the DS6000 address the challenge?
The DS6000 overcomes the architectural limits and bottlenecks which developed over time in the ESS due to the increasing number of I/Os and MB/sec from application servers.
In this section we go through the different layers and discuss how they have changed to address performance in terms of throughput and I/O rates.
11.3.1 Fibre Channel switched disk interconnection at the back end
Because SSA connectivity has not been further enhanced to increase the connectivity speed beyond 40MB/sec, Fibre Channel connected disks were chosen for the DS6000 back end. This technology is commonly used to connect a group of disks in a
FC-AL shortcomings
There are some shortcomings with plain
As the term arbitration implies, each individual disk within an
Another challenge which is not adequately solved is the handling of failures within the
A third issue with conventional
For highly parallel operations, concurrent reads and writes with various transfer sizes, this impacts the total effective bandwidth of an
How DS6000 series overcomes FC-AL shortcomings
The DS6000 uses the same Fibre Channel drives as used in conventional
These switches use
Chapter 11. Performance considerations | 223 |