• All devices used to connect iSCSI devices must support 9K jumbo frames. Every switch, router, WANaccelerator, and any other network device that handles iSCSI traffic must support 9K jumbo frames. Ifyou are not sure that every device in your iSCSI network supports 9K jumbo frames, then do not turnon jumbo frames.• Devices on both sides (server and SAN) must have jumbo frames enabled. It is recommended that anychange to the jumbo frames enabled/disabled setting is conducted during a maintenance window.• If MTU frame is not set correctly on the data paths, then devices cannot communicate. Packets thatare larger than MTU size are discarded and do not reach the destination.• QLogic 4010 series cards do not support jumbo frames.Perform the following steps in the Dell Storage Manager Client to display the model number of an iSCSII/O card:1. Use the Dell Storage Manager Client to connect to the Storage Center.2. Click the Hardware tab.3. From the Hardware tab navigation pane, click the Controllers node.4. In the right pane, click the IO Ports tab.5. In the iSCSI area of the IO Ports tab, the Description column displays the model numbers of theiSCSI I/O cards.Other iSCSI SettingsThe following settings are Dell recommended iSCSI settings and best practices.Table 24. Recommended iSCSI HBA SettingsSetting iSCSI Best PracticeFull Duplex • Use auto-negotiate for all interfaces that negotiate at full-duplex and at themaximum speed of the connected port (1GbE or 10GbE).• If a switch cannot correctly auto-negotiate at full-duplex or at the maximumspeed of the connection, it should be hard set at full-duplex and at themaximum speed of the connected port (1GbE or 10GbE).MTU Verify the optimal MTU setting for replications. The default is 1500 but sometimesWAN circuits or VPNs create additional overhead that can cause packetfragmentation. This fragmentation may result in iSCSI replication failure and/orsuboptimal performance. Adjust the MTU setting using the Dell Storage ManagerClient.Switch • Configure switch interfaces that connect directly to servers or storage systemsto forward using PortFast or Edgeport. Go to the Switch Configuration Guidespage and refer to the guide for the current switch.• Ensure that any switches used for iSCSI are of a non-blocking design.• When deciding which switches to use, remember that you are running iSCSItraffic over the switch. Use only quality, managed, enterprise-class networkingequipment. It is not recommended to use SBHO (small business/home office)class equipment outside of lab/test environments. Check the Dell StorageCompatibility Matrix to ensure it has been fully tested to work in a SAN.VLAN • To find best practices, go to the Switch Configuration Guides page and refer tothe guide for the current switch.• Maintain two separate VLANs when using multipathed iSCSI.• Disable unicast storm control on every switch that handles iSCSI traffic.180 iSCSI Settings
