Deployment Guide

Connect optional expansion enclosures
ME4 Series controller enclosures support 2U12, 2U24, and 5U84 expansion enclosures. 2U12 and 2U24 expansion enclosures
can be intermixed, however 2U expansion enclosures cannot be intermixed with 5U84 expansion enclosures in the same storage
system.
NOTE: To add expansion enclosures to an existing storage system, power down the controller enclosure before connecting
the expansion enclosures.
● ME4 Series 2U controller enclosures support up to ten 2U enclosures (including the controller enclosure), or a maximum of
240 disk drives.
● ME4 Series 5U controller enclosures support up to four 5U enclosures (including the controller enclosure), or a maximum of
336 disk drives.
● ME4 Series expansion enclosures are equipped with dual-IOMs. These expansion enclosures cannot be cabled to a controller
enclosure equipped with a single IOM.
● The enclosures support reverse SAS cabling for adding expansion enclosures. Reverse cabling enables 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.
Cable requirements for expansion enclosures
ME4 Series supports 2U12, 2U24, and 5U84 form factors, each of which can be configured as a controller enclosure or an
expansion enclosure. Key enclosure characteristics include:
NOTE:
To add expansion enclosures to an existing storage system, power down the controller enclosure before connecting
the expansion enclosures.
● When connecting SAS cables to IOMs, use only supported HD mini-SAS x4 cables.
● Qualified HD mini-SAS to HD mini-SAS 0.5 m (1.64 ft.) cables are used to connect cascaded enclosures in the rack.
● The maximum enclosure cable length that is allowed in any configuration is 2 m (6.56 ft.).
● When adding more than two expansion enclosures, you may need to purchase additional cables, depending upon the number
of enclosures and cabling method used.
● You may need to order additional or longer cables when reverse-cabling a fault-tolerant configuration.
Per common convention in cabling diagrams, the controller enclosure is shown atop the stack of connected expansion
enclosures. In reality, you can invert the order of the stack for optimal weight and placement stability in the rack. The schematic
representation of cabling remains unchanged. See Mount the enclosures in the rack on page 15 for more detail.
When connecting multiple expansion enclosures to an expansion enclosure, use reverse cabling to ensure the highest level of
fault tolerance.
The ME4 Series identifies controller modules and IOMs by enclosure ID and IOM ID. In the following figure, the controller
modules are identified as 0A and 0B, the IOMs in the first expansion enclosure are identified as 1A and 1B, and so on. Controller
module 0A is connected to IOM 1A, with a chain of connections cascading down (blue). Controller module 0B is connected to
the lower IOM (9B), of the last expansion enclosure, with connections moving in the opposite direction (green). Reverse cabling
enables any expansion enclosure to fail—or be removed—while maintaining access to other enclosures.
NOTE: The cabling diagrams show only relevant details such as module face plate outlines and expansion ports.
Cabling connections between a 2U controller enclosure and 2U expansion enclosures on page 19 shows the maximum cabling
configuration for a 2U controller enclosure with 2U expansion enclosures.
18
Mount the enclosures in the rack