Changing Iscsi Interface Parameters And The Impact On Load Balancing; Vrrp Load Balancing Algorithm For Selecting Gigabit Ethernet Interfaces; Configuring Load Balancing Using Vrrp - Cisco AP775A - Nexus Converged Network Switch 5010 Configuration Manual

Chapter 50 Configuring iSCSI
S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m
A Gigabit Ethernet interface configured for iSLB can only be in one VRRP group because redirected
Caution
sessions do not carry information about the VRRP IP address or group. This restriction allows the slave
port to uniquely identify the VRRP group to which it belongs.

Changing iSCSI Interface Parameters and the Impact on Load Balancing

All iSCSI interfaces in a VRRP group that has load balancing enabled must have the same interface
VSAN, authentication, proxy initiator mode, and forwarding mode. When you need to change any of
these parameters for the iSCSI interfaces in a VRRP group, you must do so one interface at a time.
During the transition time when the parameter is changed on some interfaces in the VRRP group and not
the others, the master port does not redirect new initiators and instead handles them locally.
Changing the VSAN, proxy initiator, authentication, and forwarding mode for iSCSI interfaces in a
Caution
VRRP group can cause sessions to go down multiple times.

VRRP Load Balancing Algorithm For Selecting Gigabit Ethernet Interfaces

When the VRRP master receives an iSCSI session request from an initiator, it first checks for an existing
mapping to one of the interfaces in that VRRP group. If such a mapping exists, the VRRP master
redirects the initiator to that interface. If no such mapping exists, the VRRP master selects the least
loaded interface and updates the selected interface's load with the initiator's iSLB metric (weight).
The VRRP master interface is treated specially and it takes lower load compared to the other interfaces.
Note
This is to account for the redirection work performed by the master interface for every session. A new
initiator is assigned to the master interface only if the following is true for every other interface:
VRRP backup interface load > [2 * VRRP master interface load + 1]

Configuring Load Balancing Using VRRP

You must first configure VRRP on the Gigabit Ethernet interfaces on the switch that connect to the IP
network before configuring VRRP for iSLB. For information on how to configure VRRP on a Gigabit
Ethernet interface, see the
To configure VRRP load balancing using Device Manager, follow these steps:
Choose IP > iSCSI iSLB.
Step 1
You see the iSCSI iSLB dialog box (see
Click the VRRP tab.
Step 2
Click Create to configure VRRP load balancing for iSLB initiators.
Step 3
You see the Create iSCSI iSLB VRRP dialog box shown in
OL-17256-03, Cisco MDS NX-OS Release 4.x
"Virtual Router Redundancy Protocol" section on page
Figure 50-30).
Cisco MDS 9000 Family Fabric Manager Configuration Guide
51-8.
Figure 50-34.
Configuring iSLB
50-45