Cabling the enclosure, Redundancy vs. nonredundancy, Single sas in-port configurations – Dell PowerVault MD3000 User Manual
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Cabling Your RAID Enclosure
Each MD3000 RAID controller module also contains a SAS Out port connector. This port allows you the
option to connect the RAID enclosure to an expansion enclosure.
Cabling the Enclosure
You can cable your enclosure to up to four hosts and up to two expansion enclosures. The configuration
that you choose depends on the number of hosts you have, whether you are connecting to a standalone
host or a cluster node, and the level of data redundancy that you need.
The figures that follow are grouped according to the number of SAS In port connectors available on the
MD3000. Single SAS In port configurations and dual SAS In port configurations each support redundant
and nonredundant cabling.
Redundancy vs. Nonredundancy
Nonredundant configurations, configurations that provide only a single data path from a host to the
RAID enclosure, are recommended only for non-critical data storage. Path failure from a failed or
removed cable, a failed host bus adapter, or a failed or removed RAID controller module results in loss of
host access to storage on the RAID enclosure.
Redundancy is established by installing separate data paths between the host and the storage array, in
which each path is to different RAID controller modules. Redundancy protects the host from losing
access to data in the event of path failure, because both RAID controllers can access all the disks in the
storage array.
Single SAS In-Port Configurations
Figure 2-1 through Figure 2-5 show supported nonredundant and redundant cabling configurations to
MD3000 RAID controller modules with a single SAS In port connector. Each diagram shows the
maximum number of optional expansion enclosures attached.
Figure 2-1 through Figure 2-3 show one and two hosts, each connected to only one RAID controller
module that is subsequently expanded to two more storage enclosures. The hosts can share storage space
but without redundant paths, if one path were to fail, the server on that path would be disconnected
from the storage array.