Host Bus Adapters - Dell PowerVault MD3000 Hardware Owner's Manual

The multi-path software identifies the existence of multiple paths to a virtual disk and establishes a
preferred path to that disk. If any component in the preferred path fails, the multi-path software
automatically re-routes I/O requests to the alternate path so that the storage array continues to operate
without interruption.
NOTE:
Multi-path software is included with MD Storage Manager.
Preferred and Alternate Controllers and Paths
A preferred controller is a RAID controller module designated as the owner of a virtual disk or disk group.
The preferred controller is automatically selected by MD Storage Manager when a virtual disk is created.
You can change the preferred RAID controller module owner of a virtual disk after it is created.
Ownership of a virtual disk is moved from the preferred controller to the second controller (also called
the alternate controller) when the preferred controller is:
• Physically removed
• Updating firmware
• Involved in a fatal event that caused failover over to the alternate controller
Paths used by the preferred controller to access either the disks or the host are called the preferred paths;
redundant paths are called the alternate paths. If a failure causes the preferred path to become
inaccessible, the storage array automatically uses the alternate path to access data.

Host Bus Adapters

Each cable connection from a host to a RAID controller module is made through an HBA. The HBA is
installed in the host and provides an interface to the internal bus of the host. To configure for highest
redundancy, you must use more than one HBA in a single host. You can connect each HBA to the RAID
controller modules (preferred and alternate) to ensure that the server data will be accessible even if one
HBA fails.
Selecting Host Bus Adapters for Redundancy
NOTE:
For maximum redundancy, you must select all HBA host ports connected to the array when manually
defining host topology or setting up host mapping.
You can have multiple SAS HBA host ports-to-array connections for each host. When setting up host
mapping, you must select the HBA host ports from the list of Known HBA host ports in MD Storage
Manager. Add all of the HBA host ports to the list of Selected HBA host port identifiers/aliases for the
host for which you are defining the LUN mapping.
For example, a host might have two HBAs, each with two HBA host ports connected to the array. For this
host, you would select all four HBA host ports.
Using Your RAID Enclosure
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