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In-the-Lab: Full ESX/vMotion Test Lab in a Box, Part 3

August 21, 2009

Creating Zvols for iSCSI Targets

NexentaStor has two facilities for iSCSI targets: the default, userspace based target and the Common Multiprotocol SCSI Target (COMSTAR) option. Besides technical differences, the biggest difference in the COMSTAR method versus the default is that COMSTAR delivers:

  • LUN masking and mapping functions
  • Multipathing across different transport protocols
  • Multiple parallel transfers per SCSI command
  • Compatibility with generic HBAs (i.e. Fiber Channel)
  • Single Target, Multiple-LUN versus One Target per LUN

To enable COMSTAR, we need to activate the NexentaStor Console from the web GUI. In the upper right-hand corner of the web GUI page you will find two icons: Console and View Log. Clicking on “Console” will open-up an “NVM Login” window that will first ask for your “Admin” user name and password. These are the “admin” credentials configured during installation. Enter “admin” for the user and whatever password your chose then click “Login” to continue.

Login to the NexentaStor Console using the administrative username and password established during installation.

Login to the NexentaStor Console using the administrative user name and password established during installation.

Now we will delve briefly to command-line territory. Issue the following command at the prompt:

setup iscsi target comstar show

The NexentaStor appliance should respond by saying “COMSTAR is currently disabled” meaning the system is ready to have COMSTAR enabled. Issue the following command at the prompt to enable COMSTAR:

setup iscsi target comstar enable

After a few seconds, the system should report “done” and COMSTAR will be enabled and ready for use. Enter “exit” at the command line, press enter and then close the NMV window.

Enabling the COMSTAR target system in NexentaStor.

Enabling the COMSTAR target system in NexentaStor.

With COMSTAR successfully enabled, we can move on to creating our iSCSI storage resources for use by VMware. In our lab configuration we have two storage pools from which any number of iSCSI LUNs and NFS folders can be exported. To create our first iSCSI target, let’s first create a container for the target – and its snapshots – to reside in. From the NexentaStor “Data Management” menu, select “Shares” and, from the Folders area, click on the “Create” link.

The “Create New Folder” panel allows us to select volume0 as the source volume, and we are going to create a folder named “target0” within a folder named “targets” directly off of the volume root by entering “targets/target0” in the “Folder Name” box. Because our iSCSI target will be used with VMware, we want to set the default record size of the folder to 64K blocks, leave compression off and accept the default case sensitivity. While Zvols can be created directly off of the volume root, SOLORI’s best practice is to confine each LUN to a separate folder unless using the COMSTAR plug-in (which is NOT available for the Developer’s Edition of NexentaStor.)

Since 80GB does not allow us a lot of breathing room in VMware, and since vCenter 4 allows us to “thin provision” virtual disks anyway, we want to “over-subscribe” our volume0 by telling the system to create a 300GB iSCSI target. If we begin to run out of space, NexentaStor will allow us to add new disks or redundancy groups without missing taking the target or storage pool off-line (online capacity expansion).

To accomplish this task, we jump back to the “Settings” panel, click on the “Create” link within the “iSCSI Target” sub-panel, select volume0 as the source volume, enter “targets/target0/lun0” as the “Zvol Name” with a “Size” of 300GB and – this is important – set “Initial Reservation” to “No” (thin provisioning), match the record size to 64KB, leave compression off and enable the target by setting “iSCSI Shared” to “Yes.” Now, click “Create zvol” and the iSCSI LUN is created and documented on the page that follows. Clicking on the zvol’s link reports the details of the volume properties:

Zvol Properties immediately after creation.

Zvol Properties immediately after creation.

Now let’s create some NFS exports – one for ISO images and one for virtual machines…

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5 comments

  1. […] subsequent virtual ESX/ESXi instance(s). We will provision the storage similarly to the NFS storage we created in Part 3 of this series. To activate this file system, we need to go back to the NexentaStor web GUI and select “Data […]

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  3. […] Easy as 1,2,3Preview: Install ESXi 4.0 to FlashIn-the-Lab: Full […]      by In-the-Lab: Full ESX/vMotion Test Lab in a Box, Part 3 « SolutionOriented Blog September 29, 2009 at 7:08 […]

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  4. […] Part 3, Building and Provisioning the VSA […]

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  5. Thanks for this post. While I knew quiet a lot about the Nexentastor VSA by playing with it, I found a few jewel of information, that will help me rebuild a better VSA.
    Thanks for the time and effort you put in this article.

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