A computer connected to a remote hard disk via iscsi is referred to as an iscsi initiator.

When managing your gateway, you work with volumes or virtual tape library (VTL) devices that are exposed as Internet Small Computer System Interface (iSCSI) targets. For Volume Gateways, the iSCSI targets are volumes. For Tape Gateways, the targets are VTL devices. As part of this work, you do such tasks as connecting to those targets, customizing iSCSI settings, connecting from a Red Hat Linux client, and configuring Challenge-Handshake Authentication Protocol (CHAP).

Topics

• Connecting Your VTL Devices to a Windows client
• Connecting Your Volumes or VTL Devices to a Linux Client
• Customizing iSCSI Settings
• Configuring CHAP Authentication for Your iSCSI Targets

The iSCSI standard is an Internet Protocol (IP)–based storage networking standard for initiating and managing connections between IP-based storage devices and clients. The following list defines some of the terms that are used to describe the iSCSI connection and the components involved.

iSCSI initiator

The client component of an iSCSI network. The initiator sends requests to the iSCSI target. Initiators can be implemented in software or hardware. Storage Gateway only supports software initiators.

The server component of the iSCSI network that receives and responds to requests from initiators. Each of your volumes is exposed as an iSCSI target. Connect only one iSCSI initiator to each iSCSI target.

The software program on Microsoft Windows computers that enables you to connect a client computer (that is, the computer running the application whose data you want to write to the gateway) to an external iSCSI-based array (that is, the gateway). The connection is made using the host computer's Ethernet network adapter card. The Microsoft iSCSI initiator has been validated with Storage Gateway on Windows 8.1, Windows 10, Windows Server 2012 R2, Windows Server 2016, and Windows Server 2019. The initiator is built into these operating systems.

The iscsi-initiator-utils Resource Package Manager (RPM) package provides you with an iSCSI initiator implemented in software for Red Hat Linux. The package includes a server daemon for the iSCSI protocol.

Each type of gateway can connect to iSCSI devices, and you can customize those connections, as described following.

Connecting Your VTL Devices to a Windows client

A Tape Gateway exposes several tape drives and a media changer, referred to collectively as VTL devices, as iSCSI targets. For more information, see Requirements.

You connect only one application to each iSCSI target.

The following diagram highlights the iSCSI target in the larger picture of the Storage Gateway architecture. For more information on Storage Gateway architecture, see How Tape Gateway works (architecture).

To connect your Windows client to the VTL devices

1. On the Start menu of your Windows client computer, enter iscsicpl.exe in the Search Programs and files box, locate the iSCSI initiator program, and then run it.

   You must have administrator rights on the client computer to run the iSCSI initiator.

2. If prompted, choose Yes to start the Microsoft iSCSI initiator service.

3. In the iSCSI Initiator Properties dialog box, choose the Discovery tab, and then choose Discover Portal.

4. In the Discover Target Portal dialog box, enter the IP address of your Tape Gateway for IP address or DNS name, and then choose OK. To get the IP address of your gateway, check the Gateway tab on the Storage Gateway console. If you deployed your gateway on an Amazon EC2 instance, you can find the public IP or DNS address in the Description tab on the Amazon EC2 console.

   For gateways that are deployed on an Amazon EC2 instance, accessing the gateway over a public internet connection is not supported. The Elastic IP address of the Amazon EC2 instance cannot be used as the target address.

5. Choose the Targets tab, and then choose Refresh. All 10 tape drives and the media changer appear in the Discovered targets box. The status for the targets is Inactive.

   The following screenshot shows the discovered targets.

6. Select the first device and choose Connect. You connect the devices one at a time.

7. In the Connect to Target dialog box, choose OK.

8. Repeat steps 6 and 7 for each of the devices to connect all of them, and then choose OK in the iSCSI Initiator Properties dialog box.

On a Windows client, the driver provider for the tape drive must be Microsoft. Use the following procedure to verify the driver provider, and update the driver and provider if necessary.

To verify the driver provider and (if necessary) update the provider and driver on a Windows client

1. On your Windows client, start Device Manager.

2. Expand Tape drives, choose the context (right-click) menu for a tape drive, and choose Properties.

3. In the Driver tab of the Device Properties dialog box, verify that Driver Provider is Microsoft.

4. If Driver Provider is not Microsoft, set the value as follows:

   1. Choose Update Driver.

   2. In the Update Driver Software dialog box, choose Browse my computer for driver software.

   3. In the Update Driver Software dialog box, choose Let me pick from a list of device drivers on my computer.

   4. Select LTO Tape drive and choose Next.

   5. Choose Close to close the Update Driver Software window, and verify that the Driver Provider value is now set to Microsoft.

5. Repeat steps 4.1 through 4.5 to update all the tape drives.

Connecting Your Volumes or VTL Devices to a Linux Client

When using Red Hat Enterprise Linux (RHEL), you use the iscsi-initiator-utils RPM package to connect to your gateway iSCSI targets (volumes or VTL devices).

To connect a Linux client to the iSCSI targets

1. Install the iscsi-initiator-utils RPM package, if it isn't already installed on your client.

   You can use the following command to install the package.

   sudo yum install iscsi-initiator-utils

2. Ensure that the iSCSI daemon is running.

   1. Verify that the iSCSI daemon is running using one of the following commands.

      For RHEL 5 or 6, use the following command.

      sudo /etc/init.d/iscsi status

      For RHEL 7, use the following command.

      sudo service iscsid status

   2. If the status command doesn't return a status of running, start the daemon using one of the following commands.

      For RHEL 5 or 6, use the following command.

      sudo /etc/init.d/iscsi start

      For RHEL 7, use the following command. For RHEL 7, you usually don't need to explicitly start the iscsid service.

      sudo service iscsid start

3. To discover the volume or VTL device targets defined for a gateway, use the following discovery command.

   sudo /sbin/iscsiadm --mode discovery --type sendtargets --portal [GATEWAY_IP]:3260

   Substitute your gateway's IP address for the [GATEWAY_IP] variable in the preceding command. You can find the gateway IP in the iSCSI Target Info properties of a volume on the Storage Gateway console.

   The output of the discovery command will look like the following example output.

   For Volume Gateways: [GATEWAY_IP]:3260, 1 iqn.1997-05.com.amazon:myvolume

   For Tape Gateways: iqn.1997-05.com.amazon:[GATEWAY_IP]-tapedrive-01

   Your iSCSI qualified name (IQN) will be different than what is shown preceding, because IQN values are unique to an organization. The name of the target is the name that you specified when you created the volume. You can also find this target name in the iSCSI Target Info properties pane when you select a volume on the Storage Gateway console.

4. To connect to a target, use the following command.

   Note that you need to specify the correct [GATEWAY_IP] and IQN in the connect command.

   For gateways that are deployed on an Amazon EC2 instance, accessing the gateway over a public internet connection is not supported. The Elastic IP address of the Amazon EC2 instance cannot be used as the target address.

   sudo /sbin/iscsiadm --mode node --targetname iqn.1997-05.com.amazon:[ISCSI_TARGET_NAME] --portal [GATEWAY_IP]:3260,1 --login

5. To verify that the volume is attached to the client machine (the initiator), use the following command.

   ls -l /dev/disk/by-path

   The output of the command will look like the following example output.

   lrwxrwxrwx. 1 root root 9 Apr 16 19:31 ip-[GATEWAY_IP]:3260-iscsi-iqn.1997-05.com.amazon:myvolume-lun-0 -> ../../sda

   For Volume Gateways only: We highly recommend that after you set up your initiator, you customize your iSCSI settings as discussed in Customizing Your Linux iSCSI Settings.

Customizing iSCSI Settings

After you set up your initiator, we highly recommend that you customize your iSCSI settings to prevent the initiator from disconnecting from targets.

By increasing the iSCSI timeout values as shown in the following steps, you make your application better at dealing with write operations that take a long time and other transient issues such as network interruptions.

Before making changes to the registry, you should make a backup copy of the registry. For information on making a backup copy and other best practices to follow when working with the registry, see Registry best practices in the Microsoft TechNet Library.

Topics

• Customizing Your Windows iSCSI Settings
• Customizing Your Linux iSCSI Settings
• Customizing Your Linux Disk Timeout Settings for Volume Gateways

Customizing Your Windows iSCSI Settings

For a Tape Gateway setup, connecting to your VTL devices by using a Microsoft iSCSI initiator is a two-step process:

1. Connect your Tape Gateway devices to your Windows client.

2. If you are using a backup application, configure the application to use the devices.

The Getting Started example setup provides instructions for both these steps. It uses the Symantec NetBackup backup application. For more information, see Connecting Your VTL Devices and Configuring NetBackup Storage Devices.

To customize your Windows iSCSI settings

1. Increase the maximum time for which requests are queued.

   1. Start Registry Editor (Regedit.exe).

   2. Navigate to the globally unique identifier (GUID) key for the device class that contains iSCSI controller settings, shown following.

      Make sure that you are working in the CurrentControlSet subkey and not another control set, such as ControlSet001 or ControlSet002.

      HKEY_Local_Machine\SYSTEM\CurrentControlSet\Control\Class\{4D36E97B-E325-11CE-BFC1-08002BE10318}

   3. Find the subkey for the Microsoft iSCSI initiator, shown following as [.

      The key is represented by a four-digit number, such as 0000.

      HKEY_Local_Machine\SYSTEM\CurrentControlSet\Control\Class\{4D36E97B-E325-11CE-BFC1-08002BE10318}\[

      Depending on what is installed on your computer, the Microsoft iSCSI initiator might not be the subkey 0000. You can ensure that you have selected the correct subkey by verifying that the string DriverDesc has the value Microsoft iSCSI Initiator, as shown in the following example.

   4. To show the iSCSI settings, choose the Parameters subkey.

   5. Open the context (right-click) menu for the MaxRequestHoldTime DWORD (32-bit) value, choose Modify, and then change the value to 600.

      This value represents a hold time of 600 seconds. The example following shows the MaxRequestHoldTime DWORD value with a value of 600.

2. You can increase the maximum amount of data that can be sent in iSCSI packets by modifying the following parameters:

   • FirstBurstLength controls the maximum amount of data that can be transmitted in an unsolicited write request. Set this value to 262144 or the Windows OS default, whichever is higher.

   • MaxBurstLength is similar to FirstBurstLength, but it sets the maximum amount of data that can be transmitted in solicited write sequences. Set this value to 1048576 or the Windows OS default, whichever is higher.

   • MaxRecvDataSegmentLength controls the maximum data segment size that is associated with a single protocol data unit (PDU). Set this value to 262144 or the Windows OS default, whichever is higher.

   Different backup software can be optimized to work best using different iSCSI settings. To verify which values for these parameters will provide the best performance, see the documentation for your backup software.

3. Increase the disk timeout value, as shown following:

   1. Start Registry Editor (Regedit.exe), if you haven't already.

   2. Navigate to the Disk subkey in the Services subkey of the CurrentControlSet, shown following.

      HKEY_Local_Machine\SYSTEM\CurrentControlSet\Services\Disk

   3. Open the context (right-click) menu for the TimeOutValue DWORD (32-bit) value, choose Modify, and then change the value to 600.

      This value represents a timeout of 600 seconds. The example following shows the TimeOutValue DWORD value with a value of 600.

4. To ensure that the new configuration values take effect, restart your system.

   Before restarting, you must make sure that the results of all write operations to volumes are flushed. To do this, take any mapped storage volume disks offline before restarting.

Customizing Your Linux iSCSI Settings

After setting up the initiator for your gateway, we highly recommend that you customize your iSCSI settings to prevent the initiator from disconnecting from targets. By increasing the iSCSI timeout values as shown following, you make your application better at dealing with write operations that take a long time and other transient issues such as network interruptions.

Commands might be slightly different for other types of Linux. The following examples are based on Red Hat Linux.

To customize your Linux iSCSI settings

1. Increase the maximum time for which requests are queued.

   1. Open the /etc/iscsi/iscsid.conf file and find the following lines.

      node.session.timeo.replacement_timeout = [replacement_timeout_value] 
      node.conn[0].timeo.noop_out_interval = [noop_out_interval_value] 
      node.conn[0].timeo.noop_out_timeout = [noop_out_timeout_value] 

   2. Set the [replacement_timeout_value] value to 600.

      Set the [noop_out_interval_value] value to 60.

      Set the [noop_out_timeout_value] value to 600.

      All three values are in seconds.

      The iscsid.conf settings must be made before discovering the gateway. If you have already discovered your gateway or logged in to the target, or both, you can delete the entry from the discovery database using the following command. Then you can rediscover or log in again to pick up the new configuration.

      iscsiadm -m discoverydb -t sendtargets -p [GATEWAY_IP]:3260 -o delete

2. Increase the maximum values for the amount of data that can be transmitted in each response.

   1. Open the /etc/iscsi/iscsid.conf file and find the following lines.

      node.session.iscsi.FirstBurstLength = [replacement_first_burst_length_value] 
      node.session.iscsi.MaxBurstLength = [replacement_max_burst_length_value]
      node.conn[0].iscsi.MaxRecvDataSegmentLength = [replacement_segment_length_value]

   2. We recommend the following values to achieve better performance. Your backup software might be optimized to use different values, so see your backup software documentation for best results.

      Set the [replacement_first_burst_length_value] value to 262144 or the Linux OS default, whichever is higher.

      Set the [replacement_max_burst_length_value] value to 1048576 or the Linux OS default, whichever is higher.

      Set the [replacement_segment_length_value] value to 262144 or the Linux OS default, whichever is higher.

      Different backup software can be optimized to work best using different iSCSI settings. To verify which values for these parameters will provide the best performance, see the documentation for your backup software.

3. Restart your system to ensure that the new configuration values take effect.

   Before restarting, make sure that the results of all write operations to your tapes are flushed. To do this, unmount tapes before restarting.

Customizing Your Linux Disk Timeout Settings for Volume Gateways

If you are using a Volume Gateway, you can customize the following Linux disk timeout settings in addition to the iSCSI settings described in the preceding section.

To customize your Linux disk timeout settings

1. Increase the disk timeout value in the rules file.

   1. If you are using the RHEL 5 initiator, open the /etc/udev/rules.d/50-udev.rules file, and find the following line.

      ACTION=="add", SUBSYSTEM=="scsi" , SYSFS{type}=="0|7|14", \ 
      RUN+="/bin/sh -c 'echo [timeout] > /sys$$DEVPATH/timeout'"  

      This rules file does not exist in RHEL 6 or 7 initiators, so you must create it using the following rule.

      ACTION=="add", SUBSYSTEMS=="scsi" , ATTRS{model}=="Storage Gateway", 
      RUN+="/bin/sh -c 'echo [timeout] > /sys$$DEVPATH/timeout'"

      To modify the timeout value in RHEL 6, use the following command, and then add the lines of code shown preceding.

      sudo vim /etc/udev/rules.d/50-udev.rules

      To modify the timeout value in RHEL 7, use the following command, and then add the lines of code shown preceding.

      sudo su -c "echo 600 > /sys/block/[device name]/device/timeout"

   2. Set the [timeout] value to 600.

      This value represents a timeout of 600 seconds.

2. Restart your system to ensure that the new configuration values take effect.

   Before restarting, make sure that the results of all write operations to your volumes are flushed. To do this, unmount storage volumes before restarting.

3. You can test the configuration by using the following command.

   udevadm test [PATH_TO_ISCSI_DEVICE]

   This command shows the udev rules that are applied to the iSCSI device.

Configuring CHAP Authentication for Your iSCSI Targets

Storage Gateway supports authentication between your gateway and iSCSI initiators by using Challenge-Handshake Authentication Protocol (CHAP). CHAP provides protection against playback attacks by periodically verifying the identity of an iSCSI initiator as authenticated to access a volume and VTL device target.

CHAP configuration is optional but highly recommended.

To set up CHAP, you must configure it both on the Storage Gateway console and in the iSCSI initiator software that you use to connect to the target. Storage Gateway uses mutual CHAP, which is when the initiator authenticates the target and the target authenticates the initiator.

To set up mutual CHAP for your targets

1. Configure CHAP on the Storage Gateway console, as discussed in To configure CHAP for a VTL device target on the Storage Gateway console.

2. In your client initiator software, complete the CHAP configuration:

   • To configure mutual CHAP on a Windows client, see To configure mutual CHAP on a Windows client.

   • To configure mutual CHAP on a Red Hat Linux client, see To configure mutual CHAP on a Red Hat Linux client.

To configure CHAP for a VTL device target on the Storage Gateway console

In this procedure, you specify two secret keys that are used to read and write to a virtual tape. These same keys are used in the procedure to configure the client initiator.

1. In the navigation pane, choose Gateways.

2. Choose your gateway, and then choose the VTL Devices tab to display all your VTL devices.

3. Choose the device that you want to configure CHAP for.

4. Provide the requested information in the Configure CHAP Authentication dialog box.

   1. For Initiator Name, enter the name of your iSCSI initiator. This name is an Amazon iSCSI qualified name (IQN) that is prepended by iqn.1997-05.com.amazon: followed by the target name. The following is an example.

      iqn.1997-05.com.amazon:your-tape-device-name

      You can find the initiator name by using your iSCSI initiator software. For example, for Windows clients, the name is the value on the Configuration tab of the iSCSI initiator. For more information, see To configure mutual CHAP on a Windows client.

      To change an initiator name, you must first disable CHAP, change the initiator name in your iSCSI initiator software, and then enable CHAP with the new name.

   2. For Secret used to Authenticate Initiator, enter the secret requested.

      This secret must be a minimum of 12 characters and a maximum of 16 characters long. This value is the secret key that the initiator (that is, the Windows client) must know to participate in CHAP with the target.

   3. For Secret used to Authenticate Target (Mutual CHAP), enter the secret requested.

      This secret must be a minimum of 12 characters and a maximum of 16 characters long. This value is the secret key that the target must know to participate in CHAP with the initiator.

      The secret used to authenticate the target must be different than the secret to authenticate the initiator.

   4. Choose Save.

5. On the VTL Devices tab, confirm that the iSCSI CHAP authentication field is set to true.

To configure mutual CHAP on a Windows client

In this procedure, you configure CHAP in the Microsoft iSCSI initiator using the same keys that you used to configure CHAP for the volume on the console.

1. If the iSCSI initiator is not already started, on the Start menu of your Windows client computer, choose Run, enter iscsicpl.exe, and then choose OK to run the program.

2. Configure mutual CHAP configuration for the initiator (that is, the Windows client):

   1. Choose the Configuration tab.

      The Initiator Name value is unique to your initiator and company. The name shown preceding is the value that you used in the Configure CHAP Authentication dialog box of the Storage Gateway console.

      The name shown in the example image is for demonstration purposes only.

   2. Choose CHAP.

   3. In the iSCSI Initiator Mutual Chap Secret dialog box, enter the mutual CHAP secret value.

      In this dialog box, you enter the secret that the initiator (the Windows client) uses to authenticate the target (the storage volume). This secret allows the target to read and write to the initiator. This secret is the same as the secret entered into the Secret used to Authenticate Target (Mutual CHAP) box in the Configure CHAP Authentication dialog box. For more information, see Configuring CHAP Authentication for Your iSCSI Targets.

   4. If the key that you entered is fewer than 12 characters or more than 16 characters long, an Initiator CHAP secret error dialog box appears.

      Choose OK, and then enter the key again.

3. Configure the target with the initiator's secret to complete the mutual CHAP configuration.

   1. Choose the Targets tab.

   2. If the target that you want to configure for CHAP is currently connected, disconnect the target by selecting it and choosing Disconnect.

   3. Select the target that you want to configure for CHAP, and then choose Connect.

   4. In the Connect to Target dialog box, choose Advanced.

   5. In the Advanced Settings dialog box, configure CHAP.

      1. Select Enable CHAP log on.

      2. Enter the secret that is required to authenticate the initiator. This secret is the same as the secret entered into the Secret used to Authenticate Initiator box in the Configure CHAP Authentication dialog box. For more information, see Configuring CHAP Authentication for Your iSCSI Targets.

      3. Select Perform mutual authentication.

      4. To apply the changes, choose OK.

   6. In the Connect to Target dialog box, choose OK.

4. If you provided the correct secret key, the target shows a status of Connected.

To configure mutual CHAP on a Red Hat Linux client

In this procedure, you configure CHAP in the Linux iSCSI initiator using the same keys that you used to configure CHAP for the volume on the Storage Gateway console.

1. Ensure that the iSCSI daemon is running and that you have already connected to a target. If you have not completed these two tasks, see Connecting to a Linux Client.

2. Disconnect and remove any existing configuration for the target for which you are about to configure CHAP.

   1. To find the target name and ensure it is a defined configuration, list the saved configurations using the following command.

      sudo /sbin/iscsiadm --mode node

   2. Disconnect from the target.

      The following command disconnects from the target named myvolume that is defined in the Amazon iSCSI qualified name (IQN). Change the target name and IQN as required for your situation.

      sudo /sbin/iscsiadm --mode node --logout GATEWAY_IP:3260,1 iqn.1997-05.com.amazon:myvolume

   3. Remove the configuration for the target.

      The following command removes the configuration for the myvolume target.

      sudo /sbin/iscsiadm --mode node --op delete --targetname iqn.1997-05.com.amazon:myvolume

3. Edit the iSCSI configuration file to enable CHAP.

   1. Get the name of the initiator (that is, the client you are using).

      The following command gets the initiator name from the /etc/iscsi/initiatorname.iscsi file.

      sudo cat /etc/iscsi/initiatorname.iscsi

      The output from this command looks like this:

      InitiatorName=iqn.1994-05.com.redhat:8e89b27b5b8

   2. Open the /etc/iscsi/iscsid.conf file.

   3. Uncomment the following lines in the file and specify the correct values for username, password, username_in, and password_in.

      node.session.auth.authmethod = CHAP
      node.session.auth.username = username
      node.session.auth.password = password
      node.session.auth.username_in = username_in
      node.session.auth.password_in = password_in

      For guidance on what values to specify, see the following table.

      Configuration Setting	Value
      username	The initiator name that you found in a previous step in this procedure. The value starts with iqn. For example, iqn.1994-05.com.redhat:8e89b27b5b8 is a valid username value.
      password	The secret key used to authenticate the initiator (the client you are using) when it communicates with the volume.
      username_in	The IQN of the target volume. The value starts with iqn and ends with the target name. For example, iqn.1997-05.com.amazon:myvolume is a valid username_in value.
      password_in	The secret key used to authenticate the target (the volume) when it communicates to the initiator.

   4. Save the changes in the configuration file, and then close the file.

4. Discover and log in to the target. To do so, follow the steps in Connecting to a Linux Client.