68 InstallationFigure 55 Cabling connections between a 2U controller enclosure and 2U expansion enclosuresThe diagram above (left) shows reverse cabling of a DS Series dual-controller 2U enclosure and supported DSEXP 2U drive enclosures configured with dual expansion modules. Controller module 0A is connected toexpansion module 1A, with a chain of connections cascading down (blue). Controller module 0B is connected tothe lower expansion module (9B), of the last expansion enclosure, with connections moving in the oppositedirection (green). Reverse cabling allows any expansion enclosure to fail—or be removed—while maintainingaccess to other enclosures.The diagram at right (above) shows the same storage components connected to use straight-through cabling. Usingthis method, if an expansion enclosure fails, the enclosures that follow the failed enclosure in the chain are nolonger accessible until the failed enclosure is repaired or replaced.The 2U drive enclosures shown in the above figure can either be of the same type or they can be a mixture of DSEXP 2U models. Given that supported 2U drive enclosure models use 12Gb/s SAS link-rate and SAS 3.0expanders, they can be ordered in desired sequence within the system, following the controller enclosure. Themiddle SAS ports on expansion modules are not used. See also Figure 21 (page 29) and the IMPORTANT entrybeneath that figure. Refer to these diagrams when cabling multiple DS EXP expansion enclosures together with DSSeries controller enclosures.DS Series does not support intermixing of DS EXP and D3284 expansion enclosures when configuring a storagesystem. Representative examples showing supported configurations and configuration limits are provided aboveController AController B1A1B2A2B0A0B3A3B9A9BReverse cabling Straight-through cablingController AController B0A0B1A1B2A2B3A3B9A9BAdd enclosures up to maximum (10) Add enclosures up to maximum (10)A CCA CC AA CC AAC AA CC AA CC AA CC AC AA CAC
