Checklist: Troubleshooting iSCSI

Please keep in mind that there are a number of ways to implement Internet Small Computer System Interface (iSCSI). This checklist assumes that you are using Microsoft's iSCSI Initiator. |

Checklist: Troubleshooting iSCSI

Verify connectivity

• iSCSI is a protocol designed to send SCSI commands over a TCP/IP network. Therefore, if TCP/IP-level connectivity does not exist, then iSCSI cannot function.

• If you can verify connectivity, but iSCSI still does not work, then make sure you don't have a firewall that's blocking TCP port 3260.

Determine if iSCSI has failed completely

The next step in the troubleshooting process is to determine whether or not you have a complete iSCSI failure. A complete failure is usually indicated when the iSCSI Initiator

displays a constant "Reconnecting" status message. A partial iSCSI failure would be a situation in which connectivity is intermittent or performance is poor.

If connectivity is intermittent or performance is poor, there are several things you can check.

• Verify that the connection between the server and the storage mechanism is not being flooded by other TCP/IP traffic.

• Run a dedicated line between the server and the storage device if possible. If a dedicated connection is not possible or practical, then place the server and the storage

device on a separate subnet from the rest of the network.

• Verify that your server has two network interface cards (NICs). One NIC should be used only for iSCSI communications, and the other should be used for communications with the

rest of the network.

• Make sure your server's network card is TOE-enabled. TOE (TCP offload engine) enabled cards offload TCP/IP functionality from the system's processor. Although many

TCP/IP applications don't get much of a performance gain from TOE, iSCSI is a big exception. iSCSI receives a tremendous performance boost from TOE in most situations.

What to do if iSCSI will not initialize

• Open the iSCSI properties sheet and select the Active Sessions tab. Disconnect any active sessions that may be listed. Next, select the Persistent Targets tab and disconnect

any persistent targets. Finally, select the Target Portals tab and remove any existing target portals.

• From the Target Portals tab, click the Add button to specify a new target portal. Enter the IP address for the target portal and enter 3260 as the socket number.

• Click the Advanced button to reveal the Advanced Settings properties sheet. Select the Microsoft iSCSI Indicator option from the Local Adapter drop down list. Verify that the source

IP matches the IP address assigned to the NIC that the server is using for iSCSI communications.

• Select the Available Targets tab and click the Logon button. When the Log On to Target dialog box appears, verify that the Automatically Restore This Connection When The System

Boots check box is selected. Microsoft also recommends selecting the Enable Multi-path check box, even if you do not have a multi-path configuration.

• Click the Advanced button. When the Advanced Settings dialog box appears, verify that the Microsoft iSCSI Initiator option is selected and that the IP address corresponding with

the correct NIC has been chosen.

• Once you have completed this process, reboot the system. You can verify that you were able to re-establish connectivity by checking the Status section of the Active Sessions tab on

the iSCSI Initiator properties sheet.

ABOUT THE AUTHOR:   Go back to checklist

Brien Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Windows 2000 Server and IIS. Brien has served as the CIO for a nationwide chain of hospitals and was once in charge of IT security for Fort Knox. As a freelance technical writer he has written for Microsoft, CNET, ZDNet, MSD2D, Relevant Technologies and other technology companies. You can visit Brien's personal Web site at http://www.brienposey.com.

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