IBM DS6000 Series manual DS6000 switched FC-AL implementation, Disk enclosure

	Fibre channel switch
Controller 0	Controller 1
	device
device
	adapter
adapter
	Fibre channel switch

Figure 2-8 Disk enclosure

When a connection is made between the device adapter and a disk, the connection is a switched connection that uses arbitrated loop protocol. This means that a mini-loop is created between the device adapter and the disk. Figure 2-9depicts four simultaneous and independent connections, one from each device adapter port.

	Switched connections
	Fibre channel switch
Controller 0	Controller 1
	device
device
	adapter
adapter
	Fibre channel switch

Figure 2-9 Disk enclosure switched connections

DS6000 switched FC-AL implementation

For a more detailed look at how the switched disk architecture expands in the DS6000, refer to Figure 2-10 on page 32. It depicts how the DS6000 is divided into two disk loops. The server enclosure (which contains the first 16 DDMs) is on loop 0. The first expansion enclosure is placed on loop 1. This allows for the best performance since we are now using all four ports on the device adapter chipset. Expansion is achieved by adding expansion enclosures onto each loop, until each loop has four enclosures (for a total of 128 DDMs). The server enclosure is the first enclosure on loop 0, which is why we can only add a total of seven expansion enclosures.

Chapter 2. Components 31