Technical information

37 EqualLogic Configuration Guide | Version 15.2 | August 2014
The actual impact on SAN throughput when using jumbo frames will depend on your workload’s I/O
characteristics.
 Support for Rapid Spanning Tree protocol (IEEE 802.1w), or edgeport or Cisco “portfast”
functionality if the SAN infrastructure will consist of more than two switches: For SAN
infrastructures consisting of more than 2 non-stacking switches, R-STP must be enabled on all ports
used for inter-switch trunks. All non-inter-switch trunk ports should be marked as “edge” ports or
set to “portfast”.
 Support for unicast storm control: iSCSI in general, and Dell EqualLogic SANs in particular can send
packets in a very “bursty” profile that many switches could misdiagnose as a virally induced packet
storm. Since the SAN should be isolated from general Ethernet traffic, the possibility of actual viral
packet storms occurring is non-existent. In an EqualLogic SAN, the switches must always pass
Ethernet packets regardless of traffic patterns.
 Support for Stacking: A switch interconnection is required to link all switches in the SAN
infrastructure together. Some Ethernet switches feature dedicated stacking interfaces. A good rule
of thumb for a dedicated stacking link bandwidth would be a minimum 20 Gbps full-duplex.
 Support for VLAN functionality
Note: It is recommended to use a physically separated network dedicated to iSCSI traffic that is not
shared with other traffic. If sharing the same physical networking infrastructure is required, then use Data
Center Bridging (DCB) for EqualLogic SAN.
 Support for creating Link Aggregation Groups (LAG): For non-stacking switches, the ability to bind
multiple physical ports into a single logical link for use as an interconnection is required. The switch
should support designating one or more ports for interconnection (via LAGs). The switch should
support creation of LAGs consisting of at least eight 1Gbps ports or at least two 10Gbps ports.
Variants of LAG (such as VLT, vPC, etc.) are also supported.
Note: For 1GbE SANs, using non-stacking switches to connect three or more EqualLogic arrays into a
single group may negatively impact SAN I/O throughput performance.
8.2.1 Connecting SAN switches in a Layer 2 network
EqualLogic storage requires that the SAN be configured as a single Layer 2 network. Layer 2 refers to the
data link layer in the OSI model (http://en.wikipedia.org/wiki/OSI_model). When more than one SAN
switch is required, each switch connected to the array group members will be in the same subnet. These
switches must be interconnected to provide a single switched Ethernet fabric. Figure 4 shows the two
common methods for interconnecting switches, using either stacking switches or non-stacking switches.