Figure 7. Connectivity topology with four hosts
For topologies with four or more hosts, SAS Y-cables are required to connect the hosts to the drive
enclosure. The SAS Y-cable allows two hosts be connected to one SAS port on the ESM. The Y-cables
and standard cables are mutually exclusive, that is, either Y-cables or standard cables can be used to
connect the hosts to the same drive enclosure, but not both.
The SAS zoning feature of the D1212 and D1224 specifies how multiple hosts access drives in the
enclosures. If SAS zoning is disabled, all attached hosts can access all drives in the enclosures, which is
typically used in standalone single-host or clustered multi-host environments, where all cluster nodes need
access to all drives. If SAS zoning is enabled, each connected host has exclusive access to a predefined
set of drives, and multiple hosts are isolated from each other.
Note: Attachment of more than one host to the same enclosure without SAS zoning is supported with
HBAs only (RAID controllers are not supported). While all attached hosts are capable of accessing all
drives in the enclosures, the clustering software running on the hosts controls which cluster nodes have
access to the drives at any given time.
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