White Papers

Connectivity considerations
12 Dell EMC PowerVault ME4 Series and VMware vSphere | 3922-BP-VM
3.2.1 iSCSI fabric settings
This section details recommended and required settings when creating an iSCSI-based SAN.
Note: 1 Gb iSCSI is supported only with the 10GBaseT controller and not the converged network controller.
3.2.1.1 Flow control settings
Ethernet flow control is a mechanism for temporarily pausing data transmission when data is being
transmitted faster than its target port can accept the data. Flow control allows a switch port to stop network
traffic sending a PAUSE frame. The PAUSE frame temporarily pauses transmission until the port is again
able to service requests.
The following settings are recommended when enabling flow control:
• A minimum of receive (RX) flow control should be enabled for all switch interfaces used by servers or
storage systems for iSCSI traffic.
• Symmetric flow control should be enabled for all server interfaces used for iSCSI traffic. ME4 Series
automatically enables this feature.
3.2.1.2 Jumbo frames
Jumbo frames increase the efficiency of Ethernet networking and reduce CPU load by including a larger
amount of data in each Ethernet packet. The default Ethernet packet size, or MTU (maximum transmission
unit), is 1,500 bytes. With Jumbo frames, this is increased to 9,000 bytes.
Note: PowerVault ME4 Series storage supports a maximum 8900-byte payload, allowing 100 bytes of
overhead for the MTU of 9000.
When enabling Jumbo frames, all devices in the path must be enabled for Jumbo frames for this frame size to
be successfully negotiated. This included server NICs or iSCSI HBAs, switches, and the ME4 Series storage.
In a vSphere environment, this also included the virtual switches and VMkernel adapters configured for iSCSI
traffic.
To enable Jumbo frames on the ME4 Series system, click System Settings > Ports > Advanced Settings
and select the Enable Jumbo Frames check box.
3.2.1.3 Jumbo frames and flow control
Some switches have limited buffer sizes and can support either Jumbo frames or flow control, but cannot
support both at the same time. If you must choose between the two features, it is recommended to choose
flow control.
Note: All switches listed in the Dell EMC Storage Compatibility Matrix support Jumbo frames and flow control
at the same time.
3.2.2 Fibre Channel zoning
Fibre Channel zones are used to segment the fabric to restrict access. A zone contains paths between
initiators (server HBAs) and targets (storage array front-end ports). Either physical ports (port zoning) on the
Fibre Channel switches or the WWNs (name zoning) of the end devices can be used in zoning. It is
recommended to use name zoning because it offers better flexibility. With name zoning, server HBAs and
storage array ports are not tied to specific physical ports on the switch.