•
All devices used to connect iSCSI devices must support 9K jumbo frames. Every switch, router, WAN accelerator, and any other
network device that handles iSCSI traffic must support 9K jumbo frames. If you are not sure that every device in your iSCSI network
supports 9K jumbo frames, then do
not
turn on jumbo frames.
•
Devices on both sides (server and SAN) must have jumbo frames enabled. It is recommended that any change 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 that are 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 Storage Manager to display the model number of an iSCSI I/O card:
1
Use Storage Manager 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 the iSCSI I/O cards.
Other iSCSI Settings
The following tables lists Dell recommended iSCSI settings and best practices.
Table 23. Recommended iSCSI HBA Settings
Setting
iSCSI Best Practice
Full Duplex
•
Use auto-negotiate for all interfaces that negotiate at full-duplex and at the maximum speed of the
connected port (1 GbE or 10 GbE).
•
If a switch cannot correctly auto-negotiate at full-duplex or at the maximum speed of the connection, it
should be hard set at full-duplex and at the maximum speed of the connected port (1 GbE or 10 GbE).
MTU
Verify the optimal MTU setting for replications. The default is 1500 but sometimes WAN circuits or VPNs
create additional overhead that can cause packet fragmentation. This fragmentation may result in iSCSI
replication failure and/or suboptimal performance. Adjust the MTU setting using Storage Manager.
Switch
•
Configure switch interfaces that connect directly to servers or storage systems to forward using PortFast
or Edgeport. Go to the
wiki page 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 iSCSI traffic over the switch. Use
only quality, managed, enterprise-class networking equipment. It is not recommended to use SBHO (small
business/home office) class equipment outside of lab/test environments. Check the
Compatibility Matrix for SC, PS, and FS Series Arrays
to ensure it has been fully tested to work in a SAN.
VLAN
•
To find best practices for a VLAN, go to the
wiki page and refer to the guide
for the current switch.
•
Maintain two separate VLANs when using multipathed iSCSI.
•
Disable unicast storm control on every switch that handles iSCSI traffic.
•
Disable multicast at the switch level for all iSCSI VLANs. Set multicast storm control to enabled (if
available) when multicast cannot be disabled.
iSCSI Settings
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