Chapter 3. Planning 53
3.6.4  Back-end storage zones
Create one Storwize V7000 storage zone for each back-end storage subsystem that is 
virtualized by the Storwize V7000.
A storage controller can present LUNs to the Storwize V7000 (as MDisks) and to other hosts 
in the SAN. However, if this is the case, it is better to allocate different ports on the back-end 
storage for communication with Storwize V7000 and for hosts traffic.
All nodes in a system must connect to the same set of storage system ports on each device. 
A system that contains any two nodes that cannot connect to the same set of storage-system 
ports is considered degraded. In this situation, a system error is logged that requires a repair 
action. This rule can have important effects on a storage system. For example, an IBM 
DS4000® series controller can have exclusion rules that determine to which host bus adapter 
(HBA) worldwide node names (WWNNs) to which a storage partition can be mapped.
In the example that is shown in Figure 3-3, all back-end storage ports are connected to all 
Storwize V7000 ports. Therefore, each port on back-end storage is zoned to all ports of the 
Storwize V7000 that are connected to the same fabric. For clarity, the figure shows only paths 
for one back-end storage port per controller: Port P1 in Fabric 0 and port P4 in Fabric 1. 
Figure 3-3   Example of back-end storage subsystem zoning
There might be particular zoning rules governing attachment of specific back-end storage 
systems. Review guidelines at this website to verify whether you must consider other policies 
when planning zoning for your back-end systems.
Note: You can use more than four fabric ports per node to improve peak load I/O 
performance. However, if a node receives more than 16 logins from another node, it 
causes node error 860. To avoid this error, you must use zoning, port masking, or 
combination of the two. For more information, see 3.6.7, “Port designation 
recommendations” on page 58, 3.6.8, “Port masking” on page 59, and the IBM Storwize 
V7000 documentation.