Many organizations rely on large storage arrays and a storage area network to support their virtualized infrastructure,...
but buying expensive storage devices might not be the best choice for midsize businesses, especially if their applications do not require high IOPS. Microsoft offers several virtualized storage formats for midsize and large organizations that can reduce the need for expensive storage devices, including the iSCSI Target Server.
ISCSI Target Server runs on Windows Server 2012 and later OSes, and implements virtual storage through industry standards protocols, such as Storage Management Initiative Specification (SMI-S). System Center Virtual Machine Manager (SCVMM) can manage an iSCSI Target Server as well as a storage area network (SAN) and other storage devices.
The iSCSI Target component was first made available as a free download to run on Windows Server 2008 R2. Later, Microsoft decided to include iSCSI Target Server to play a File and Storage Services role in Windows Server 2012, eliminating the need to download it separately. Let's take a closer look at how you can manage iSCSI Target Server running on a Windows Server 2012 R2 operating system (OS).
Benefits of using iSCSI Target Server
ISCSI Target Server is the best virtualized storage option for midsize businesses. Although it requires an OS license, it eliminates the need to buy expensive SANs. While several organizations are in the process of reducing the total cost of IT through virtualization, SANs can actually increase the overall cost, because of the expertise needed to set up and manage storage. Since this feature acts as a network-accessible block-based storage device, it can simplify management. ISCSI Target Server has many use cases; most notably, it can be used to implement Hyper-V failover clusters and achieve high availability for virtualized workloads. The only situation in which iSCSI Target Server is not recommended is when working with a resource-intensive application, which requires more storage IOPS.
Enabling iSCSI Target component
As stated earlier, the iSCSI Target component ships as a File and Storage Services role in Windows Server 2012 and later OSes. To enable iSCSI Target Server, identify a Windows Server 2012 or later OS that can act as a block-storage device, launch Server Manager and then select the "iSCSI Target" component under "File and Storage Services." Once the iSCSI Target role is installed, you can create iSCSI virtual disks from the existing storage -- you can use a LUN from a SAN or other storage -- and make these disks available to SCVMM as storage pools.
Adding and managing iSCSI Target Server via SCVMM
To manage a newly added iSCSI Target Server via SCVMM, navigate to the "Fabrics" pane in the SCVMM console, right click on the "Storage" node and then click on the "Add Storage Devices," which launches the wizard shown in Figure A.
When it comes to selecting a storage provider, there are several options available. Since this feature uses SMI-S and Windows Management Instrumentation (WMI) protocols for communication, you'll need to select the "SAN and NAS devices discovered and managed by SMI-S provider" option as seen in Figure A.
Next, you need to specify the IP Address of the iSCSI Target Server. Select "SMI-S WMI" as the protocol and choose a RunAs account that has permission to connect to iSCSI Target Server and access storage pools. Click "Next" for VMM to communicate with iSCSI Target Server, as seen in Figure B.
When you click "Next," SCVMM will connect to iSCSI Target Server and then display a list of available storage pools. From here, select the storage pools that you would like SCVMM to manage and then click "Next." You can see details, such as the iSCSI Target Server name and which storage pools you added under SCVMM management, on the "Summary" page shown in Figure C. Finally, click "Finish" to add iSCSI Target as a managed storage device under SCVMM.
Note that SCVMM uses the "Add-SCStorageProvider" PowerShell cmdlet to add a storage provider, including iSCSI Target Server. If you want to use PowerShell to add the iSCSI Target Server, run the PowerShell commands shown below on VMM server:
$RunAsAccount = Get-SCRunAsAccount –Name "AdminAccount"
Add-SCStorageProvider -ComputerName "WIN-6I280B1H1QM.scvmm.local" -Name "WIN-6I280B1H1QM.scvmm.local" -RunAsAccount $RunAsAccount -AddSmisWmiProvider –RunAsynchronously
Once iSCSI Target Server is added under SCVMM management, you can create disks from available storage pools and use those disks as shared storage for deploying Hyper-V VMs. To verify the addition of iSCSI Target Server under SCVMM, navigate to the "Providers" sub-node under the "Storage" node as shown in Figure D.
The status should appear as "Responding" -- this means SCVMM is able to communicate with the iSCSI Target Server.
It's important to note that SCVMM communicates with the iSCSI Target Server using a Run As account that you specify during the "Add Storage Devices Wizard." In the event you see the status as "Not Responding," make sure the iSCSI Target Server is reachable by SCVMM and you are using a Run As account with the appropriate permission to connect to the iSCSI Target Server. If you need to change the Run As account SCVMM uses to communicate with the iSCSI Target Server, do so by navigating to the property of the storage provider as shown in Figure E.
Does SCVMM manage iSCSI Target Server differently?
SCVMM doesn't list that the target server is running an iSCSI Target Server. This is because SCVMM uses standard storage protocols -- SMI-S and symmetric multiprocessing -- to connect to a storage provider. It won't know whether the target storage device is running as an iSCSI Target Server. Since this feature uses "SMI-S WMI" protocol, SCVMM will display the provider type as "SMI-S WMI," as shown in Figure D, and uses all SMI-S functions to manage storage pools on the iSCSI Target Server.
While iSCSI Target Server can be a useful option for midsize organizations requiring virtual storage, it is not recommended for organizations that run resource-intensive applications, such as SQL and Exchange, that require more storage IOPS than iSCSI Target Server provides. It's worth mentioning that Microsoft is planning further enhancements to iSCSI Target Server and Storage Spaces in its upcoming Windows Server 2016 OS. Storage Spaces Direct in Windows Server 2016 will enable users to build highly available storage by using local storage, therefore eliminating the need for shared serial-attached iSCSI infrastructure.
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