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This command will extract all files in a folder named iscsitarget-0.4.14. Then, go to this folder by using the # cd iscsitarget-0.4.14 command. It's also very important to export the correct path for your kernel version's source. This can be done by issuing the following command:
# export KERNELSRC= /usr/src/nels/2.6.18-1.2798.fc6-i586
| iSCSI Refresher |
| iSCSI is a protocol that allows you to use SCSI commands over an IP network. It supports a Gigabit Ethernet interface at the physical layer, which lets you connect storage supporting iSCSI directly to the Gigabit switch so that the data moves from source to destination or vice versa at a very high speed. iSCSI has two main components-target and a controller. A target exposes the storage LUNs over the IP network so that the controller can discover them using an iSCSI initiator. It can then add them as the machine's local storage. So while it appears as a local storage, it's actually networked storage behind the scenes. When an iSCSI storage target device receives a read/write request, it generates the SCSI (I/O) command and then sends an IP packet over an Ethernet connection. At the receiving end (controller), the SCSI (I/O) commands are separated from the request, and then sent to the ISCSI target storage device. iSCSI will also return a response to the request using the same protocol. |
Now, compile the iSCSI target software on this FC 6 machine as follows:
# make && make install
Once you have complied the iSCSI target on the target, you have to configure it according to your requirement. For this issue the command:
# cp etc/ietd.conf /etc
Next open /etc/ietd.conf in a text editor and scroll down till you get to the “Lun 0 path” entry and change the path of the partition that you have designated for iSCSI target.
In our case, the iSCSI partition was /dev/hda2, so we changed it to “Lun 0 path=/dev/hda2”. Save this file and start the iSCSI target service on this machine as follows:
# /etc/init.d/iscsi-target start
If you want to start this service automatically when this target machine boots up issue the following command:
# chkconfig iscsi-target on
With this your target is ready. Similarly, add as many machines as you want to your storage pool.
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| Add all iSCSI targets to your initiator running on the controller machine, and then use the pool of total storage |
Configuring the controller
To access the iSCSI storage, which is being exposed by the target machines on the IP network, you need to install a software called iSCSI initiator on the controller machine. This is available for both Windows and Linux. We used the Microsoft iSCSI initiator, which can be freely downloaded from http://tinyurl.com/ywtw3.
Install this software on your controller and you will get the Microsoft initiator icon on your desktop. Double click on it and you will get its interface with four tabs (General, Discovery, Targets, Persistent Target and Bound volumes/devices). Go to the Discovery tab and add the iSCSI target you have setup. Then select “Targets” tab and you will find all target names with their status. On the same screen come down and select the Logon button. You will get a popup screen with the logon to target options. Here enable “Automatically restore this computer when the system boots” and click Ok.
Then apply the settings.
Now go to your Management Console and open Disk Management. If you've setup the target machines in the initiator correctly, you should see a new drive in your Disk Management. You can format this storage or create a new partition, or do whatever else you do to a normal local drive. This drive will be treated like an ordinary local drive, even though it's being accessed over the network. You can share this partition on your local LAN so that network users can use it for file sharing or whatever else you want them to use it for.
iSCSI targets for Windows
Instead of using FC 6, you can also use Windows. The concept remains the same. You just have to find the right iSCSI target software for your OS. There are quite a few iSCSI targets available for Windows, both from Microsoft and other vendors. If you use the Microsoft iSCSI target, then there is a catch. Microsoft iSCSI target only runs on the Windows 2003 Storage Server, and the latter is not available as a commercial product. It's only sold to OEMs.
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| You will see all targets as inactive. To make them active for all iSCSI targets, you need to login each target from the initiator |
We also tried another commercial iSCSI target, called MySAN. We've carried it on this month's CD as well for you to try out. It's very easy to use. A simple setup wizard guides you through its installation. But the real work starts after it's installed. Start MySAN from Program Files and go to the third tab which says “Target”. Here select the partition/disk which you want to share over iSCSI. Now click on the Add button to format the partition. This will also ask you for the “Target name”. Give it a suitable name. This name will also represent the Share. After you click on OK, the software will format your partition so make sure you don't have any valuable data on it. Once the format is done go to the tab called “Hosts”. Here you have to add the Host or the initiator which is going to use the iSCSI share. Click on the add button and a new window will open. Here fill in the Initiator node name. This name should be exactly the same as the name of the initiator node given in the iSCSI initiator software such as Microsoft iSCSI initiator. After you have done this, again go back to the “Targets” and select the drive which you have just formatted. A drop down at the bottom of the window will be highlighted. Click on the drop down box and you will see the Initiator you have just added. Select it. Now go to the “General” tab, select the Network card on which you want to let the share happen and click on the “On” radio button. That's it. The configuration is done.
Now go to the machine on which you want to mount this iSCSI share. Install MS iSCSI initiator on it exactly as you did in the previous (Linux) section. You will get the Microsoft initiator icon on your desktop. Start the application interface and select the discovery tab and add the ISCSI target you have you have created. You can do that by providing the IP address or the machine name of the target machine. Now select “Targets” tab and you will find the all target names with their status. Now select the Logon button. You will get a popup screen with the logon to target options. Here enable “Automatically restore this computer when the system boots” and click ok and then apply the settings. The volume will be available in the initiator machine.
That was about how to build a very basic SAN. You can use it to create a common storage pool out of ordinary machines. In the next issue, we'll move further in this and tell you how to build your own storage cluster.
Anindya Roy and Sanjay Majumder
Source: PCQuest
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