Types Of Redundancy For Front-End Connections - Dell SC4020 Deployment Manual

Figure 43. Legacy Mode Cabling Example
1. Server 1
3. Switch 1
5. Storage system
7. Storage controller 2
NOTE: To use multiple paths simultaneously, the server must be configured to use MPIO.

Types of Redundancy for Front-End Connections

Front-end redundancy is achieved by eliminating single points of failure that could cause a server to lose
connectivity to the Storage Center.
Depending on how the Storage Center is cabled and configured, the following types of redundancy are
available.
Table 4. Redundancy and Failover Behavior
Redundancy
Asymmetric Logical Unit
Access (ALUA)
Port redundancy
Storage controller
redundancy
Path redundancy
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Failover Behavior
If a storage controller becomes unavailable, all the standby paths on the
other storage controller become active.
In virtual port mode, if a single port becomes unavailable, the port can move
to another available port in the same fault domain.
If a storage controller becomes unavailable, the ports on the offline storage
controller can move to the available storage controller.
When multiple paths are available from a server to a storage system, a server
configured for multipath I/O (MPIO) can use multiple paths for I/O. If a path
becomes unavailable, the server continues to use the remaining available
paths.
2. Server 2
4. Switch 2
6. Storage controller 1
Connect the Front-End Cabling