Building A High-Availability San - Dell EqualLogic PS6100 series Configuration Manual

Table 25 Stacking vs. Inter-Switch Trunking
Interconnect
type
Stacking
Link
Aggregation
Groups (LAG)
7.3

Building a high-availability SAN

Designing a redundant SAN requires the availability of redundant NICs or HBAs on each server. A
redundant NIC configuration on the server requires at least two NICs installed into separate PCI slots
in the server. Table 26 below shows how to achieve redundant server NIC connection configurations
for a server with three installed NICs.
March 2013
Primary purpose
Create a larger,
logical switch within
an isolated physical
location.
Create a data path
between switches in
one location or
subnet with those in
another location or
subnet
Dell EqualLogic Configuration Guide v14.1
Analysis
Advantages:
Easier to manage multiple switches as single
switch
Higher bandwidth than using link aggregation
and Ethernet
Not limited by Ethernet standards
Concerns:
Proprietary, cannot be used to interconnect
switches from different vendors
Increases cost of switch
Stack bandwidth overload risk
Recommendation:
Best way to scale a storage network in a single
location on a single subnet
Provides lower latency and higher bandwidth
than inter-switch trunking
Understand the stacking technology and limit
stack size in accordance with total throughput
requirements and connection counts.
Advantages:
Leverages Ethernet standard extensions
Can be used to interconnect switches from
different vendors
Can use Link Aggregation Protocols
(LACP/EtherChannel) to pool multiple 1GbE or
10GbE links into a single logical link providing
bandwidth and redundancy
Concerns:
Most solutions limited to 8 port link
aggregation group
Spanning Tree Protocol must be used if more
than two switches are used causing some links
to be "blocked" reducing bandwidth availability
LAG bandwidth overload risk
Recommendation:
Use when stacking is not available
Use when connecting to aggregation/core
switching infrastructure
Use when switches are from different vendors
7-68