Dell PowerVault MD3000 - Manual (Page 50)

50
Using Your RAID Enclosure
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.
Host Cabling for Redundancy
To make sure that the RAID storage array remains accessible to the host, establish a minimum of two
physical paths from each host to the RAID controller modules. The following examples show host
cabling for redundancy.
One Host with Two Cable Connections
Figure 3-1 shows a single host with two HBAs. Both HBAs have two ports, but use only a single port.
Each HBA is connected to one RAID controller module in the RAID enclosure. Each RAID controller
module has one port.
Figure 3-1. One Host with Two Cable Connections
RAID controller module 1
MD3000 RAID Enclosure
dual-HBA host server
RAID controller module 0