All About iscsi. Creating an ISCI LUN

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1 All About iscsi iscsi - Internet Small Computer Systems Interface is a standard for connecting storage to computers. Its origins lie with large computer systems and it is of particular relevance to organizations that run hundreds of servers, have vast amounts of storage and require great flexibility when it comes to managing that storage. However, the exact same technology is available within QTS and may be of interest to small businesses and even home users. First, we need to consider how it operates. So far we have used shared folders on the server. For Windows users, it is possible to map drive letters to shared folders using a variety of methods; this enables us to refer to, say, \\server\home as drive H, but it is not a real drive in the sense that the C: drive is and we are simply using the letter H as a form of shorthand. With iscsi, an amount of space is set aside on the server. The server is referred to as the iscsi host and the space is known as the iscsi target, which is given a LUN (Logical Unit Number) to help reference it. A computer known as the iscsi client or initiator connects to the LUN (target), which it sees as a complete disk drive. This drive, to most intents and purposes, behaves like a real physical drive and can be partitioned, formatted and used in any way the user requires. There is a one-to-one relationship between target and initiator (in practice, if not in theory), meaning a single target should not be connected to multiple clients. It is possible to move targets from one server to another without unduly affecting the clients, hence the reason for its relevance to larger organizations with requirements for redundancy and disaster recovery. One nice thing about iscsi is that it is can be a very efficient protocol, resulting in high data transfer speeds. Creating an ISCI LUN Go into the Main Menu and launch Storage Manager. Click iscsi Storage the first time you do so you may receive a message that the iscsi service is disabled and a question as to whether you want to enable it click OK. There is then a question about launching the Quick Configuration Wizard; again, click OK. The wizard appears as follows: Figure 1: iscsi Quick Configuration Wizard

2 There are three options we want the first one so make sure iscsi Target with a mapped LUN is selected and click Next. Click Next on the second screen. On the third screen specify the Target Name keep it simple e.g. LUN1 and the Wizard will complete the rest of the entries. Click Next: Figure 2: Create new iscsi Target The fourth step of the wizard can be used to specify authentication and improve security ( CHAP authentication ). As we are all friends here, we will not do so. Click Next. Step 5 of the Wizard allows you to choose the type of iscsi LUN and to choose the volume that the LUN will be located on. If you have a single volume commonly the case on a small system then you are restricted to the first option of Create an image file on a volume as an iscsi LUN. If you have more than one volume you also have the option to Allocate space from a storage pool as an iscsi LUN; this has some advantages and flexibilities, particularly on a larger systems. We will assume the first option so click Next.

3 Figure 3: Select the iscsi LUN Type You will then be taken to Step 8. Use the Instant Allocation option, as Thin Provisioning can be problematic should the system ever run low on space. Use Capacity to specify how much space will be available in this example we have allocated 50GB, but it depends on your requirements. Click Next.

4 Figure 4: Specify the size for the LUN You will be taken to Step 12, which is a screen to confirm the settings. Click Next and the LUN will be created. Click Finish on the final screen and you will be returned to the main Storage Manager screen, where the details will be listed.

5 Connecting a Client Having set up the iscsi LUN(s) on the server, the client computer(s) can now be connected. The procedure for this varies slightly depending on the operating system this example uses a Windows 7 client. Go into the Control Panel on the PC and choose Administrative Tools and within it click iscsi Initiator. The first time you do this you may receive a message stating that the Microsoft iscsi service is not running click Yes to start the service (it will start up automatically on subsequent occasions). In the Target field on the Target tab, enter the IP address of the server and click Quick Connect. The target should be found and a status of Connected shown: Click Done and then Okay. Figure 5: Connecting to the Target

6 Go back to Administrative Tools and choose Computer Management; within it choose Disk Management. You will receive a message about having to initialize the new disk. If the disk is less than 2TB in size choose MBR, if greater than 2TB you will need to choose GPT. Click OK. Figure 6: Disk initialization The new disk will then be visible within Disk Management. Right-click it and choose New Simple Volume. Run through the Wizard to format the volume and assign a drive letter to it; thereafter it can be used as a normal disk drive.

7 LUN Backups There is special provision within Storage Manager for backing up LUNs. Go into Storage Manager and click on LUN Backup within the iscsi Storage section. Alternatively, go into Backup Station and choose LUN Backup in the Remote Replication section, which will take you to the same place. Click Create a Job to start the Wizard, choose the first option Back up an iscsi LUN and click Next. On the second panel choose the LUN and click Next. Figure 7: Creating a backup On the third panel choose the destination. If backing up to an external USB drive you would choose Local Host (the other options are to shared folders on external Windows and Linux servers). Click Next:

8 Figure 8: Select the backup destination Step 4 allows you to fine tune the location i.e. the LUN(s) to be backed up, but the defaults are usually fine so just click Next. Step 5 is for specifying a backup schedule, as per your preferences. Continue working through the steps of the Wizard and you will reach a Confirm Settings panel; if all is well click Next followed by Finish on the next screen.