Four Servers Connected To Dual 12 Gb 4-Port Sas Storage Controllers - Dell SC4020 Deployment Manual

If a storage controller becomes unavailable, the volume becomes active on the other storage controller.
The state of the paths on the available storage controller are set to Active/Optimized and the state of the
paths on the other storage controller are set to Standby. When the storage controller becomes available
again and the ports are rebalanced, the volume moves back to its preferred storage controller and the
ALUA states are updated.
If a SAS path becomes unavailable, the Active/Optimized volumes on that path become active on the
other storage controller. The state of the failed path for those volumes is set to Standby and the state of
the active path for those volumes is set to Active/Optimized.
NOTE: Failover in SAS virtual port mode occurs within a single fault domain. Therefore, a server
must have both connections in the same fault domain. For example, if a server is connected to SAS
port 2 on one storage controller, it must be connected to SAS port two on the other storage
controller. If a server is not cabled correctly when a storage controller or SAS path becomes
unavailable, access to the volume is lost.

Four Servers Connected to Dual 12 Gb 4-Port SAS Storage Controllers

A storage system with four 12 Gb front-end SAS ports on each storage controller can connect to up to
four host servers, if each host server has one HBA with dual SAS ports.
About this task
This configuration includes four fault domains spread across both storage controllers. The storage
controllers are connected to each host server using two SAS connections.
If a storage controller becomes unavailable, all of the standby paths on the other storage controller
become active.
Steps
1. Connect fault domain 1 (shown in orange) to host server 1.
a. Connect a SAS cable from storage controller 1: port 1 to the SAS HBA on host server 1.
b. Connect a SAS cable from storage controller 2: port 1 to the SAS HBA on host server 1.
2. Connect fault domain 2 (shown in blue) to host server 2.
a. Connect a SAS cable from storage controller 1: port 2 to the SAS HBA on host server 2.
b. Connect a SAS cable from storage controller 2: port 2 to the SAS HBA on host server 2.
3. Connect fault domain 3 (shown in gray) to host server 3.
a. Connect a SAS cable from storage controller 1: port 3 to the SAS HBA on host server 3.
b. Connect a SAS cable from storage controller 2: port 3 to the SAS HBA on host server 3.
4. Connect fault domain 4 (shown in red) to host server 4.
a. Connect a SAS cable from storage controller 1: port 4 to the SAS HBA on host server 4.
b. Connect a SAS cable from storage controller 2: port 4 to the SAS HBA on host server 4.
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Connect the Front-End Cabling