Which two statements are correct when designing a core-edge or tired storage network topologies for high availability? (Choose two)

High availability in core-edge SANs is achieved through redundancy at multiple levels. The most fundamental principle is deploying the entire network topology in pairs, creating two independent and isolated fabrics (Fabric A and Fabric B). This macro-level redundancy ensures that the failure of any single component or even an entire fabric does not cause a loss of connectivity.

At a micro-level, within the switches themselves, distributing Inter-Switch Links (ISLs) across independent ASICs provides hardware fault tolerance. If a single ASIC fails, the ISLs connected to other ASICs on the same switch will maintain the connection between the core and edge layers, preventing the ASIC from becoming a single point of failure.

B. Large port count switches are commonly used in the core but are not restricted to it; their use at the edge is a valid design choice.

C. For high availability, a trunk of multiple links is superior to a single faster link, as it provides path redundancy if one link fails.

1. Cisco Systems, "Cisco MDS 9000 Family Best Practices," White Paper, C11-740385-01, May 2018.

Page 6, Section: SAN Topology: "The recommended SAN design for high availability is a dual-fabric SAN. In this design, two separate and redundant fabrics are created. The fabrics are physically isolated from each other, and there are no ISLs between them." This directly supports option D.

2. Jon Tate, et al., "IBM SAN Survival Guide," IBM Redbooks, SG24-6143-02, April 2017.

Page 70, Section 3.2.2 "Redundancy": "The most basic form of redundancy is to have two of everything... The most common way to achieve this is to create two separate fabrics (FabA and FabB)." This also supports option D.

Page 81, Section 3.2.5 "Inter-Switch Links": The guide discusses ISL trunking for performance and availability. While not explicitly mentioning ASICs, it states, "For availability, it is important to ensure that the ISLs that form a trunk are spread across different physical resources on the switch." In modular switches, these resources are port groups, ASICs, and blades, directly supporting the principle in option A.

3. Broadcom Inc., "Brocade SAN Design Guide," GA-DG-033-00, October 2011.

Page 21, Section: Designing for Availability: "The most important design consideration for availability is redundancy. The goal is to eliminate all single points of failure... The standard method for achieving this is to deploy two completely separate, redundant fabrics." This is another strong reference for option D. The guide further details distributing ISLs across port groups on fixed-port switches and across blades on director-class switches to achieve hardware-level redundancy, which aligns with the principle of spreading links across ASICs (Option A).