IBM manual DS8000 split network, DS6000 command flow

Open systems		Storage HMC
host		CLI
CLI script
		interpreter
ESSDSCLIsoftware
		External	Dual
			internal
		network
Network interface			network
		interface
			interfaces
CS Server A	CS Server B	CLI interface		CLI interface
CS Client	CS Client
Cluster 1	Cluster 2	Server 0		Server 1
ESS 800			DS8000

Figure 11-2 DS CLI Copy Services command flow

DS8000 split network

One thing that you may notice about Figure 11-2is that the S-HMC has different network interfaces. The external network interface is an Ethernet port that must be accessible from the open systems host network interface. The dual, internal network interfaces use the two internal Ethernet switches within the DS8000 base frame to deliver the commands to the relevant storage server. This means that the DS8000 itself is not on the same network as the open systems host. The S-HMC therefore acts as a bridge between the external server network and the internal DS8000 network.

Clearly a major benefit of this setup is that the internal network within the DS8000 has no single points of failure. By using a second S-HMC it is possible to create a completely redundant communications network for the DS CLI traffic between a host server and the DS8000 servers.

DS6000 command flow

If a DS6000 is used, commands are instead issued to the DS Storage Manager PC that has to be supplied and set up when a DS6000 is installed. The DS Storage Manager PC then issues the commands to the relevant DS6000 controller. This command flow is depicted in Figure 11-3 on page 237.

236DS8000 Series: Concepts and Architecture