The correct selections are B, C, and D.
The design objective behind Huawei back-end enclosure connectivity is to distribute back-end traffic and avoid concentrating storage bandwidth, enclosure load, or failure domains on a single connection path. Consequently, disk enclosures should be distributed across multiple loops and controller back-end interface resources.
Huawei’s training material describes back-end direct-connect networking using multiple back-end interface modules and requires symmetrical interface-module/port placement. For smart disk enclosures, the uplink and downlink ports are used according to a prescribed cascade topology, and only limited cascading depth is supported. This explains the reasoning behind B, C, and D: distribute enclosures, limit the number connected on each loop, and spread loops across back-end interface modules.
Option A is incorrect because SAS disk enclosures and smart disk enclosures use different back-end connection architectures and must not simply be mixed arbitrarily within one loop.
The exact B, C, D combination is also explicitly provided in the supplied HCIE-Storage question set.
Correct back-end topology planning improves available bandwidth, preserves redundancy, and reduces performance degradation caused by excessive enclosure concentration.
Study Guide Topics: Data Storage Technology Presentation → Flash Storage Hardware → Disk Enclosures → Back-End Networking → Loop Distribution.
