This is a example of how to create an MPIO connection to an iSCSI target in a high performance environment. By high performance, we mean that we have an isolated VLAN for iSCSI traffic, and that only iSCSI traffic will travel on the VLAN. All non-essential protocols (netbios, client for microsoft networks, etc.) have been unbound from our iSCSI interfaces. We will be connecting to a target that supports active-active using the Microsoft DSM Round-Robin mode.

This document is provided as a convenience only. If you have access to the Microsoft iSCSI initiator Users Guide version 2.06 or later, you should reference that document, as it has a much more thorough treatement of this subject. Furthermore, that document should be regarded as authoritative if there are confilicts with these intstructions, unless those conflicts are specific to the way Alacritech products function.

Before starting you need to make sure that the target you plan to use supports MPIO, and that it supports active-active connections. If the target supports MPIO, but does not support active-active, you can still make an MPIO connection, but the only supported mode will be failover. There's nothing wrong with failover mode, it gives you network redundancy, but it does not provide the performance increase that the other MPIO modes do.

The other thing you should know is whether you target manufacturer has their own MPIO DSM (Device Specific Module). If they do, it may be preferable to use their DSM mode instead of using the round-robin mode that we use in this example.

Our target is an EqualLogic PS100 Storage Array with a portal address of 192.168.51.1/22. The target has 3 ethernet interfaces all on this subnet. The target has already had a volume set up, and has been configured so that our initiator host has access to it.

The inititator host is running Windows Server 2003 R2 SP2, and has the Windows iSCSI initiator version 2.07, including MPIO, installed. It has an Alacritech SES2002XT dual port iSCSI Accelerator that we will be using to connect to the target. The iSCSI interfaces are configured thusly:

C:\Temp>ipconfig
Windows IP Configuration
...
Ethernet adapter 3A_iSCSI:

   Connection-specific DNS Suffix  . :
   IP Address. . . . . . . . . . . . : 192.168.50.105
   Subnet Mask . . . . . . . . . . . : 255.255.252.0
   Default Gateway . . . . . . . . . :

Ethernet adapter 3B_iSCSI:

   Connection-specific DNS Suffix  . :
   IP Address. . . . . . . . . . . . : 192.168.50.125
   Subnet Mask . . . . . . . . . . . : 255.255.252.0
   Default Gateway . . . . . . . . . :

After opening the iSCSI initiator applet, the first thing we do is add the portal address of the PS100
 

 
Once the portal address has been entered, the available targets are displayed. It is not obvios which target we want to log on to. The only way to figure that out is to look at the configuration of the target itself. Since that process is different for each manufacturers' target, we will not cover that here. Suffice to say that we know the highlighted target is the one we want.
 

 
So we click "Log On", and check both the box for persistent connections and the box for Multi-Path.
 

 
We then select "Advanced" so that we can configure the individual connects. Set "Local adapter" to "Microsoft iSCSI Initiator", and select one of the two IP addresses on our iSCSI network as the source IP.
 

 
Next we select the destination address. On most targets we would see several destination addresses here, one for each ethernet interface, and we would chose one. The PS100 is different though. Because EqualLogic uses a technology called iSCSI redirect, we see only one address here. We select that address, and let the PS100 worry about redirecting the connection to the appropriate interface.
 

 
After hitting "OK" a couple of times, we get back to the target window which now shows as "connected".
 

 
Now we simply repeat the login process. The only difference is that this time we select a different IP source address. Had this been a target that exports all target adresseses, we would also select a different target address. As we said previously, the iSCSI redirect implementation on the PS100 makes this unnecessary.
 

 
So now we are back at our target window, and it looks no different than it did after logging on the first time. Select the target again an hit the "Details" button.
 

 
This opens the target properties pane. Now select the "Devices" tab and highlight one of the available devices.
 

 
With a device highlighted, activate the "Advanced" button to bring up the "Device Details" pane. This pane should show the "Load Balance Policy" as "Fail over only", and should show one connection as active, and one as standby.
 

 
Change the "Load Balance Policy" to "Round-Robin". All paths should immediately change to active, and your MPIO connection is now fully functional. The bandwidth to target is now equal to the sum of the bandwidth of completely independant paths. In this example, we have two completely independant paths of one gigabit each, so the bandwidth to target is two gigabit. Had we more network interfaces available we could increase the bandwidth even further.
 

 
If we now run the command netstat -nt we see that we have a connection from 192.168.50.105:2817 to 192.168.51.2:3260, and from 192.168.50.125:2819 to 192.168.51.4:3260, and that both connections are offloaded, indicating that everthing is work absolutely as it should.