MDS ISLB

This post is intended to provide an overview and some of the configuration steps involved in ISLB.

The first step is to enable the iSCSI feature.  I have older 9200's that use the 'enable' command:
MDS-1(config)# iscsi enable module 2

 The next step involves configuring IP on the interfaces and setting up VRRP:

MDS-1(config)#interface GigabitEthernet2/1.56
  ip address 198.18.56.1 255.255.255.0
  no shutdown
  vrrp 1
    priority 110
    preempt
    address 198.18.56.250
    no shutdown

VRRP can load balance the iSCSI requests across multiple MDS'es:

MDS-1(config)#islb vrrp 1 load-balance

CFS can be used to distribute the ISLB configuration to all members of the fabric.  Note that dynamically and statically mapped iSCSI initiators are not distributed though.

MDS-1(config)#islb distribute

The MDS provides a virtual target for the client initiator to use.  This target can use the pwwn of the JBOD disk.  The client initiator must be permitted to access this target either via a permit all or a permit statement using the symbolic name:

MDS-1(config)#islb virtual-target name iqn.hella.storage
  pWWN 22:00:00:14:c3:1b:a2:ba
  initiator iqn.1991-05.com.mywindows7.desktop permit

An initiator configuration is needed for the iSCSI client.  The example below uses system assigned pWWN and nWWN. 

MDS-1(config)#islb initiator name iqn.1991-05.com.mywindows7.desktop
  static pWWN system-assign 1
  static nWWN system-assign
  vsan 10

The final step is commiting the changes to the ISLB configuration.  Remember that since this is being distributed via CFS, none of the ISLB configuration is present until it is committed. 

MDS-1(config)islb commit

Zoning

In order to allow the client initiator to access the target  storage resource, we need the pWWN of the virtual target:

MDS-1# sh iscsi initiator
iSCSI Node name is iqn.1991-05.com.mywindows7.desktop
    Initiator ip addr (s): 10.10.209.250
    iSCSI alias name:
    Configured node (iSLB)
    Node WWN is 22:03:00:0d:ec:1f:bc:02 (configured)
    Member of vsans: 10
    Number of Initiator Targets: 0
    Number of Virtual n_ports: 1
    Virtual Port WWN is 22:04:00:0d:ec:1f:bc:02 (configured)
      Interface iSCSI 2/1, Portal group tag: 0x3080
      VSAN ID 10, FCID 0x0b0003

zone name ISLB-ZONE vsan 10
    member pwwn 22:04:00:0d:ec:1f:bc:02
    member pwwn 22:00:00:14:c3:1b:a2:ba
!               [J1D1]

zoneset name ISLB-ZS vsan 10
    member ISLB-ZONE
zoneset activate name ISLB-ZS vsan 10

A more simple way to zone ISLB is to use the symbolic nodename of the iniator in the zone:

MDS-1# sh zone active
zone name ISLB-ZONE vsan 10
* fcid 0x0b01e0 [pwwn 22:00:00:14:c3:1b:a2:ba] [J1D1]
* fcid 0x0b0003 [symbolic-nodename iqn.1991-05.com.mywindows7.desktop]

Verification 

The vrrp summary is a great tool:
MDS-1# sh islb vrrp summary

                         -- Groups For Load Balance --
--------------------------------------------------------------------------------
               VR Id             VRRP Address Type             Configured Status
--------------------------------------------------------------------------------
                   1                          IPv4                       Enabled

                       -- Interfaces For Load Balance --
--------------------------------------------------------------------------------
                                                             Initiator  Redirect
 VR Id         VRRP IP              Switch WWN     Interface      Load   Enabled
--------------------------------------------------------------------------------
M    1   198.18.56.250 20:00:00:0d:ec:1f:bc:00    GigE2/1.56      1000        No
       1   198.18.56.250 20:00:00:0d:ec:0e:96:c0    GigE2/1.56         0           No

                    -- Initiator To Interface Assignment --
--------------------------------------------------------------------------------
Initiator  VR Id         VRRP IP              Switch WWN               Interface
--------------------------------------------------------------------------------
iqn.1991-05.com.mywindows7.desktop
               1   198.18.56.250 20:00:00:0d:ec:1f:bc:00   GigabitEthernet2/1.56

The virtual target is another good one:

MDS-1# sh islb virtual-target
target: iqn.hella.storage
  * Port WWN 22:00:00:14:c3:1b:a2:ba
    Configured node (iSLB)
    No. of initiators permitted: 1
      initiator iqn.1991-05.com.mywindows7.desktop is permitted
    All initiator permit is disabled
    Trespass support is  disabled
    Revert to primary support is  disabled