Best Practices for EqualLogic SANs Using Cisco Nexus 2248TP (1Gb) Fabric Extender ( FEX )

Hello EQL Family,

The Cisco Nexus ecosystem is based on a virtualized chassis solution where Nexus 5000 (5k) switches
act as “fabric managers”and intelligent switches for unintelligent port expanders in the Nexus 2000 (2k)  
family that do not provide any intelligent data management, but must pass all traffic through a LAG to
one or more 5k class switches for processing.  This puts an additional burden on the interconnect
between the 2k port aggregator and the 5k fabric manager. 

The primary questions: 

• What is the impact of the Cisco Nexus architecture on EQL SAN design? 
• What are the Nexus design recommendations to ensure a high performance SAN?

This whitepaper focuses on best practice recommendations for designing and configuring an
EqualLogic SAN consisting of Nexus 5k family switches as an aggregation layer to downstream
Nexus 2k family of Fabric Extenders.
 
The goal of this paper is to answer the following questions:

1. Impact on SAN performance when arrays and hosts are attached to the same pair of FEXs?
2. Recommendations for using FEX / Switch architectures with EqualLogic?
3. Recommended configuration steps to implement that recommended architecture?

Cisco promotes a general Top of Rack/End of Row ( ToR/EoR ) deployment model for Nexus
products based on the Nexus 5k switch as an EoR switch and Nexus 2k as ToR port aggregator.

Considerations

Important considerations with Cisco Nexus Fabric Extenders and Dell EqualLogic storage are :

• The Cisco Nexus 2k Series Fabric Extenders perform no local switching.
• All traffic in and out of the switch must traverse the uplink between the Fabric Extender and the uplink switch.
• Related to the first consideration listed above, it is vital to remember that there is a potential
  oversubscription ratio of 1.2:1 on the Cisco Nexus 2248TP 1Gb Fabric Extender when all ports are utilized.

Understanding this factor is beneficial while designing the network. When designing a high throughput 
EqualLogic SAN, it is generally recommended to avoid oversubscription, however if an oversubscription
model is used, it is even more importantto recognize that performance will only be as greatas the most
restrictive bottleneck in the network path. Remember to note, EqualLogic consists of one active
controller and one passive controller, this can help avoid the oversubscription on Cisco Fabric Extenders
when active and passive connections are balanced across fabric extenders.

Remember: All traffic traversing the Fabric Extenders must be sent to the Cisco Nexus 5k for switching, 
                      the Fabric Extenders are incapable of local switching.

Note: This paper is to be used as guidance for configuring Cisco Nexus 5548UP Switches,
Cisco Nexus Fabric Extenders 2248TP, and EqualLogic PS-6000 Arraysand not intended to
be an all-inclusive document for other FEX scenarios. Other Fabric Extenders may have as
much as 12:1 oversubscription and we are concerned about this ratio of oversubscription between
the FEX and the upstream Nexus 5K switch.

We do not recommend solutions with large oversubscription ratio.  

Here is the link to the White Paper:

Best Practices for EqualLogic SANs Using Cisco Nexus 2248TP 1Gb Fabric Extender 

Until Next Time,

Twitter:    @GuyAtDell
Email:      guy_westbrook@dell.com
Chatter:  @EQL Tech Enablement

Guy

Click the link below to access the Storage Infrastructure and Solutions  (SIS)  Team publications library.
Which has all of our Best Practice White Papers, Reference Architectures, and other EQL documents:

 http://en.community.dell.com/techcenter/storage/w/wiki/2631.storage-infrastructure-and-solutions-team.aspx