Installing Enclosures
96-30065-001 Rev. A0
DataDirect Networks EF4024 FC RAID System Setup Guide | 16
2.2
Connecting the Enclosures
The EF4024 controller enclosure supports up to three expansion enclosures, or a maximum
of 96 disk drives. The EF4024 enclosures support both
straight-through
and
reverse
SAS
cabling. Reverse cabling allows any drive enclosure to fail—or be removed—while
maintaining access to other enclosures. Fault tolerance and performance requirements
determine whether to optimize the configuration for high availability or high performance
when cabling. The EF4024 controller modules support both 3-Gbps and 6-Gbps internal disk
drive speeds together with 3-Gbps and 6-Gbps expander link speeds.
CAUTION :
Some 6-Gbps disks might not consistently support a 6-Gbps transfer
rate. If this happens, the system automatically adjusts transfers to those
disks to 3 Gbps, increasing reliability and reducing error messages with
little impact on system performance. This rate adjustment persists until
the controller is restarted or power-cycled.
Cabling diagrams in this section show fault-tolerant cabling patterns. Controller and
expansion modules are identified by <enclosure-ID><controller-ID>. When connecting
multiple drive enclosures, use reverse cabling to ensure the highest level of fault tolerance,
enabling controllers to access remaining drive enclosures if a drive enclosure fails.
For example,
Figure 10
shows reverse cabling, wherein controller 0A (with enclosure-ID=0;
controller-ID=A) is connected to expansion module 1A, with a chain of connections
cascading down (blue cable). Controller 0B is connected to the lower expansion module (B)
of the last drive enclosure in the chain, with connections moving in the opposite direction
(green cable).
2.2.1
Cable Requirements
The expansion enclosures, supporting 6 Gb internal disk drive and expander link speeds, can
be attached to an EF4024 controller enclosure using supported mini-SAS to mini-SAS cables.
The EF4024 enclosures support 6-Gbps or 3-Gbps expansion port data rates. Use only
DDN-qualified cables, and observe the following guidelines:
• When connecting SAS cables to expansion modules, use only supported mini-SAS x4
cables with SFF-8088 connectors supporting your 6 Gb application
• Qualified mini-SAS to mini-SAS cables are used to connect cascaded enclosures in the
rack; the “mini-SAS to mini-SAS” cable designator connotes SFF-8088 to SFF-8088
connectors
• The maximum expansion cable length allowed in any configuration is 2 meters (6.56')
• Cables required, if not included, must be separately purchased
• When adding more than two drive enclosures, you may need to purchase additional
1-meter or 2-meter cables, depending upon number of enclosures and cabling method
used; spanning 3 or 4 drive enclosures requires 1-meter (3.28') cables
• You may need to order additional or longer cables when reverse-cabling a fault-tolerant
configuration (see
Figure 10
).
• Use only DDN-qualified cables for host connections
