C Iscsi Settings; Flow Control Settings; Ethernet Flow Control; Switch Ports And Flow Control - Dell SC4020 Deployment Manual

iSCSI Settings
This appendix lists recommended and required settings when using iSCSI cards.

Flow Control Settings

This section provides information about flow control and the recommended flow control settings.

Ethernet Flow Control

802.3x flow control is a mechanism for temporarily pausing data transmission when a NIC, an HBA port,
or a switch port is transmitting data faster than its target port can accept the data.
Ethernet flow control allows a switch port to stop network traffic between two nodes by sending a
PAUSE frame to another switch port or edge device. The PAUSE frame temporarily pauses transmission
until the port is again able to service requests.

Switch Ports and Flow Control

Recommendations for using Ethernet Flow Control depends on the switch port hardware.
• Ethernet Flow Control should be set to ON for switch ports connected to Storage Center storage
system card ports.
• Switch port settings for server NICs and other switch ports in the switch network should be set to ON.

Flow Control

Dell recommends the following settings as best practice 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. Storage
Center automatically enables this feature.
NOTE: To find best practices for iSCSI SAN switch configuration, go to the
Guides page.

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, Dell recommends
choosing flow control.
NOTE: All the switches listed in the
and flow control at the same time.
However, if you use jumbo frames, be aware of the following:
• To simplify troubleshooting initial deployments, make sure that all servers, switches, and storage are
fully operational before enabling jumbo frames.
• All devices connected through iSCSI must support 9K jumbo frames or larger.
iSCSI Settings
Dell Storage Compatibility Matrix
Switch Configuration
support both jumbo frames
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