50
Switch
Topologies
The host-to-controller tray topologies or host-to-controller-drive tray topologies
presented in this section include one or more switches. The host adapters in the hosts
might be HBAs for Fibre Channel, HCAs for InfiniBand, or Ethernet for iSCSI.
Switches are not supported for SAS host connections.
When a host is connected to a dual-controller controller-drive tray or a dual-controller
controller tray, each attached host should have two host adapters installed. For
redundancy, attach each of the host adapters to a different switch (or switch zone) so
that one switch (or zone) connects to controller A and the other to controller B in the
controller tray or the controller-drive tray. In the case where a host has one HBA and
one iSCSI Ethernet adapter, the two connections might require two different types of
switches.
One Host to a
Controller Tray or a
Controller-Drive
Tray
The following figure shows an example of a switch topology with one host, a
controller tray or a controller-drive tray, and a zoned switch. The following table
describes which of the components in this topology are non-redundant and present a
risk of a single point of failure.
ATTENTION Possible loss of data access – You must install alternate path software
or an alternate path (failover) driver on the host to support failover in the event of an
HBA failure or a host channel failure.
Table 8 Redundant and Non-Redundant Components in a Switched
Configuration with One Host and a Controller Tray or a Controller-Drive Tray
Component Redundant Non-Redundant
Host/server Non-redundant
Host adapter Redundant
Host-to-controller cable Redundant
Switch Non-redundant
Controller Redundant
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