Figure 2-7 Industry standard FC-AL disk enclosure
The main problems with standard
The full loop is required to participate in data transfer. Full discovery of the loop via LIP (loop initialization protocol) is required before any data transfer. Loop stability can be affected by DDM failures.
In the event of a disk failure, it can be difficult to identify the cause of a loop breakage, leading to complex problem determination.
There is a performance drop off when the number of devices in the loop increases.
To expand the loop it is normally necessary to partially open it. If mistakes are made, a complete loop outage can result.
These problems are solved with the switched
Switched FC-AL advantages
The DS6000 uses switched
Standard
Direct
Isolation capabilities in case of DDM failures, which provides easy problem determination
Predictive failure statistics
Simplified expansion: no cable rerouting required when adding another disk enclosure
The DS6000 architecture employs dual redundant switched
Two independent switched networks to access the disk enclosures
Four access paths to each DDM
Each device adapter port operates independently
Double the bandwidth over traditional
In the DS6000, the switch chipset is completely integrated into the controllers. Each controller contains one switch. Note, however, that the switch chipset itself is completely separate from the controller chipset. In Figure
30DS6000 Series: Concepts and Architecture
