IBM DS6000 Series manual Array sites, Physical layer as the base for virtualization

	Inter-server communication
	Device Adapter	Device Adapter
Server0	pair	Server1
	Storage enclosure	Switches
	Switched loop 1	Switched loop 2

Figure 4-1 Physical layer as the base for virtualization

When you compare this with the ESS design, where there was a real loop and having an

8-pack close to a device adapter was an advantage, this is no longer relevant for the DS6000. Because of the switching design, each drive is in close reach of the device adapter, apart from a few more hops through the Fibre Channel switches for some drives. So, it is not really

aloop, but a switched FC-AL loop with the FC-AL addressing schema: Arbitrated Loop Physical Addressing (AL-PA).

4.2.1Array sites

An array site is a group of four DDMs. What DDMs make up an array site is pre-determined by the DS6000, but note, that there is no pre-determined server affinity for array sites. The DDMs selected for an array site are chosen from the same disk enclosure string (see Figure 4-2 on page 68). All DDMs in an array site are of the same type (capacity and RPM).

Chapter 4. Virtualization concepts 67