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Both scenarios (the use of a single network and the use of two physically separate networks) are supported for Internet Small Computer System Interface (iSCSI)-based and LAN-based access networks to SAN Volume Controller. Redundant paths to volumes can be provided in both scenarios. 

For iSCSI-based access, the use of two networks and separating iSCSI traffic within the networks by using a dedicated virtual local area network (VLAN) for storage traffic prevent any IP interface, switch, or target port failure from compromising the host servers’ access to the volumes. 

A clustered system  of SAN Volume Controller nodes that are connected to the same fabric presents logical disks or volumes  to the hosts. These volumes are created from managed LUNs or managed disks  (MDisks) that are presented to SAN Volume Controller by the storage subsystems and grouped in storage pools . The following distinct zone sets are shown in the fabric: 

GLYPH<SM590000> Host zones, in which the hosts can see and address SAN Volume Controller nodes and access volumes 

GLYPH<SM590000> Storage zones, in which SAN Volume Controller nodes can see and address the MDisks/LUNs that are presented by the storage subsystems 

The logical architecture of SAN Volume Controller is shown in Figure 9-2, which also shows how different storage pools are built by grouping MDisks, and how the volumes are created from those storage pools and presented to the hosts through I/O groups (pairs of SAN Volume Controller nodes). As shown in Figure 9-2, Vol2, Vol7, and Vol8 are mirrored volumes, or volumes with two copies, with each copy in a different storage pool. For more information about volume mirroring, see “SAN Volume Controller volume mirroring” on page 366. 

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