Introduction

The requirement for cost-effective storage solutions is nothing new. Internet small computer system interface (iSCSI) isn't new either, though it seemed to be when we started implementing it on AIX® across a JS20 blade center.

This article explains how to implement iSCSI on AIX through Cisco MDS switches. You'll cover all the steps for host and SAN switch configuration for the Cisco MDS class SAN switches. The information in this article is based on actual experience. It is assumed that you have both AIX system administration and Cisco storage area network (SAN) configuration skills.

The steps in this procedure are for Cisco Fabric Manager configuration, Cisco Device Manager configuration, and AIX host configuration. We also provide a section on AIX tuning, which is optional but recommended.

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Prerequisites

The procedures for configuration of iSCSI on AIX assumes:

• AIX Version 5.2, or higher, is installed on the server or host nodes.
• All network and fiber cabling has been completed.
• Most importantly, the network configuration is complete and tested, including the ability to perform a ping test from the AIX node to the iSCSI IP port address.

The basic configuration consisted of four JS20 server nodes connected through a Cisco Catalyst network switch, which was then bridged through to a Cisco MDS 9000 SAN switch to the storage. In this application, two IBM DS-4800s were used as the back-end storage.

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Cisco Fabric Manager

Users require administrator access and a working knowledge of zoning to create the zones required for both the host nodes and the back-end storage. To enable iSCSI on the Cisco MDS SAN switch from Cisco Fabric Manager, do the following:

1. On the MDS from the Physical Attributes (bottom left) pane, select End Devices > iSCSI.
2. Select the Control tab and then iSCSI enable for all switches in the fabric.
3. Select Apply.

Zoning

Zoning in the Cisco Fabric Manager graphical user interface (GUI) should be performed in the same manner as zoning for any other device. Once the MDS is set up to handle iSCSI interfaces, you should treat it as any other end device.

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Cisco Device Manager

Perform the following steps using Device Manager on the Cisco MDS SAN switch. Users require administrator access and a working knowledge of how to configure MDS class switches through the Device Manager GUI. A general knowledge of SANs, including zoning, is recommended.

For initial MDS setup, do the following:

1. Enable the iSCSI License feature on the Cisco MDS SAN switch.
2. On the MDS, from the Admin tab, select Feature Control.
3. Enable the iscsi–vsan-interface-membership.
4. Select Apply.

At this point, the Cisco MDS switch is ready to accept iSCSI commands.

Now you'll set up the MDS port and parameters. To configure the GigE interface, do the following:

1. Locate the iSCSI port coming from the Cisco Catalyst Network Switch.
2. Right-click on the port to be configured and select Configure….
3. Select the GigE tab from the top of the configuration panel.
4. Enter the port description in the Description field.
5. Change MTU to 9000. (Changing MTU to 9000 is a recommended setting for performance, but is optional.)
6. Enter the IP address and subnet for the iSCSI port in the IP Address/Mask field.

The Cisco Catalyst Network Switch automatically fills in the subnet mask at the end of the IP address. If the subnet you are using is different from what Cisco has assumed, it might be changed manually.

1. Select the Auth method by checking either none or chap from the iscsiAuthMethod selection boxes.
2. Select Apply.

Once complete, apply all changes for each tab. The Apply button only saves the changes for the tab you are currently working in and does not carry over to the other tabs.

To configure the iSCSI interface, do the following:

1. Select the iSCSI tab from the top on the configuration panel.
2. Input the port description in the Description field.
3. Select the appropriate virtual storage area network (VSAN) from the PortVSAN from the pull-down window, or type in the appropriate VSAN number.
4. Check the Enable box under Initiator Proxy mode.
5. Select Auto for the Assignment option.
6. Select Apply.

To configure the iSCSI_TCP interface, do the following:

1. Select the iSCSI_TCP tab from the top of the configuration panel.
2. Input the correct value for the LocalTCPport.
3. Select Apply.

For MDS Initiator/Target setup, do the following:

1. From the IP pull down on the MDS, select ISCSI….
2. On the Initiator tab, select Create.
3. In the iSCSI Initiator creation box, set the iSCSI node name or IP address and the VSAN membership.
4. Check the Persistent box under Port WWN Mapping.
5. Select the Targets tab, then select Create.
6. Input the appropriate name of the target under the iSCSI Name field.
7. Select All for the Initiator Access listing.
8. Select All or check the appropriate interfaces from the Advertised Interfaces listing field.
9. Select Apply.

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AIX host configuration

Users require root-level authorization and a working knowledge of AIX system administration.

For utilization of the DS4000 family of back-end storage, the following ODM entry was required. Other storage devices might require their own unique ODM entries, though this needs to be handled on an individual basis. Be sure that the following ODM entry is present and the ODM is connected to DS4000 type storage devices:

array.iscsi.ibm-dac-V4.add

If not present, issue the following command from the command line:

odmadd array.iscsi.ibm-dac-V4.add

To configure the iscsi0 interface, a unique network interface for iSCSI needs to be created. Using SMIT, enter:

smitty -> chgiscsisw

iqn.com.ibm.po.ppd.z19c3s11e3.hostid.0972f5ec

chdev –l iscsi0 –a initiator_name=iqn.com.ibm.pok.ppd.<host shortname>.hostid.0972f5ec

The iqn.com.ibm.pok.ppd is not a typo; this is how iSCSI resolves the target storage names. Use the <host Shortname>, for example, z20c4s11e3, where e3 is the en3 interface. The host shortname and last entry in the iSCSI string should be unique to each target entry.

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/etc/iscsi/targets configuration file

There are required entries into the /etc/iscsi/targets file. In the /etc/iscsi directory, there's a targets file that requires entries for each of the iSCSI targets ports, as outlined in Cisco Device Manager. The entries have to be created in the format shown in Listing 1 below. There are also examples in the targets file for levels of access and authentication.

##################################################################
# EXAMPLE 1: iSCSI Target without CHAP(MD5) authentication
#       Assume the target is at address 192.168.3.2,
#       the valid port is 5003
#       the name of the target is iqn.com.ibm-4125-23WTT26
# The target line would look like:
# 192.168.3.2 5003 iqn.com.ibm-4125-23WWT26
  192.169.240.8 5003 iqn.com.ibm.pok.ppd.zec1xbba3.0005
  192.169.240.16 5003 iqn.com.ibm.pok.ppd.zec1xbbb3.0006
# 192.169.240.1 5003 iqn.com.ibm.pok.ppd.zec2xbba1.0003
# 192.169.240.1 5003 iqn.com.ibm.pok.ppd.zec2xbbb1.0004
#
# EXAMPLE 2: iSCSI Target with CHAP(MD5) authentication
#       Assume the target is at address 10.2.1.105
#       the valid port is 3260
#       the name of the target is iqn.com.ibm-K167-42.fc1a
#       the CHAP secret is "This is my password."
# The target line would look like:
# 10.2.1.105 3260 iqn.com.ibm-K167-42.fc1a "This is my password."
#
# EXAMPLE 3: iSCSI Target with CHAP(MD5) authentication and line continuation
#       Assume the target is at address 10.2.1.106
#       the valid port is 3260
#       the name of the target is iqn.2003-01.com.ibm:00.fcd0ab21.shark128
#       the CHAP secret is "123ismysecretpassword.fc1b"
# The target line would look like:
# 10.2.1.106 3260 iqn.2003-01.com.ibm:00.fcd0ab21.shark128 \
#               "123ismysecretpassword.fc1b"
#
#####################################################################

Input each target (storage) address created in the MDS in the following format:

192.169.240.1 5003 iqn.com.ibm.pok.ppd.z20c4s11e3.hostid.0972f5ec

Where:

• 192.169.240.1 is the iSCSI port IP address.
• iqn.com.ibm.pok.ppd is the iSCSI resolvable target address.
• z20c4s11e3 is the host en3 interface.
• hostid is input by the user.
• 0972f5ec is input by the user.

Run cfgmgr –v.

Perform an lspv command on each of the AIX nodes, and ensure that the nodes have access to all available storage.

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Optional host configuration

The following interface tuning parameters are recommended for performance on iSCSI:

tcp_recvspace=262144
tcp_sendspace=262144
rfc1323=1
jumbo frames = yes

Command-line input procedure:

ifconfig en3 down 
ifconfig en3 detach
		
chdev –a ent3 –a jumbo_frames=yes
chdev –l  en3 –a tcp_recvspace=262144
chdev –l en3 –a tcp_sendspace=262144
chdev –l en3 –a rfc1323=1
		
ifconfig en3 up

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Conclusion

After completing the steps outlined in this article, you should have access to the configured back-end storage. Go ahead and verify that all storage is present and accessible.

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Table of contents

• Introduction
• Prerequisites
• Cisco Fabric Manager
• Cisco Device Manager
• AIX host configuration
• /etc/iscsi/targets configuration file
• Optional host configuration
• Conclusion
• Resources
• About the authors
• Comments

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