Technical information

36 EqualLogic Configuration Guide | Version 15.2 | August 2014
recommends that you use it only on WANs, where bandwidth is shared with other applications and the PS
Series array uses it for time-insensitive replication traffic.
Dell recommends against using QoS on the SAN switches.
8.2 Ethernet switches and infrastructure
Any switch used in an EqualLogic SAN should meet the requirements listed in this section.
Note: For a complete list of tested and validated components see the EqualLogic Compatibility Matrix at
the following link: EqualLogic Compatibility Matrix
An EqualLogic SAN consists of one or more hosts connected to one or more PS Series arrays through a
switched Ethernet network.
Note: The minimum network configuration for a PS Series Array consists of a connection between Eth0
on each control module and a network switch. To increase performance and availability, configure
multiple network interfaces on an array and connect them to multiple switches. EqualLogic does not
support Direct Attached Storage (DAS) configurations.
To support a high performance Dell EqualLogic SAN, switches must meet the following general
requirements:
 Low latency: Switches with relatively high latency may cause SAN throughput performance to
degrade, and under high load conditions they could increase the risk of dropped connections.
 Non-blocking backplane design: SAN Switches should be able to provide the same amount of
backplane bandwidth to support full duplex communication on ALL ports simultaneously.
 Link Layer Discovery Protocol (LLDP): If any non-array devices on the SAN network have LLDP
enabled, then the switch must have LLDP support enabled. If the SAN switch does not provide LLDP
support, then disable LLDP on all non-array devices connected to the switch. For specific
instructions on disabling LLDP on your devices, refer to the user manual of the device.
 Adequate buffer space per switch port: In addition to supporting data transfers between the hosts
and the SAN, Dell EqualLogic arrays also use the SAN to support inter-array communication and
data load balancing. For this reason, the more buffer space per port that a switch can provide the
better. Due to the multitude of buffer implementations used by switch vendors, Dell cannot provide
definitive guidelines as to how much is enough. Port buffers should be designed such that data is
not lost when traffic reaches extreme levels. Due to the clustered storage traffic patterns used by the
EqualLogic SAN architecture, switches that support “cut-through” mode are not suitable for use in
an EqualLogic SAN and may actually result in lower overall SAN performance.
 Support for IEEE 802.3x flow control (passive and/or active) on ALL ports: Switches and network
interface controllers used in an EqualLogic SAN must be able to passively respond to any “pause”
frames received.
 Support for Jumbo Frames: This is not a requirement, however most iSCSI SAN implementations
should benefit from using jumbo frames and therefore it is recommend to enable Jumbo Frames.