Storage Considerations

System Center Virtual Machine Manager (VMM) supports all forms of direct attached storage (DAS), as well as providing support for a Fibre Channel or an iSCSI storage area network (SAN). This support enables you to take advantage of your investments in these infrastructures.

VMM also supports N_Port ID Virtualization (NPIV) on a Fibre Channel SAN. NPID makes uses of Host Bus Adapter (HBA) technology that creates virtual HBA ports on hosts by abstracting the underlying physical port. This enables a single physical Fibre Channel (FC) HBA port to function as multiple logical ports, each with its own identity. Each virtual machine can then attach to its own virtual HBA port and be independently zoned to a distinct and dedicated World Wide Port Name (WWPN). For more information about NPID and HBA technology, see the documentation of HBA vendors.

How SAN Transfers Work with Virtual Machine Manager

You can use VMM to perform the following types of SAN transfers between a source computer and a destination computer:

  • Store a virtual machine from a virtual machine host to a VMM library

  • Deploy a virtual machine from a VMM library to a host

    Note

    A virtual machine that is stored on a SAN is not recognized by VMM as being deployable by SAN transfer if the virtual machine was stored directly to the library when it was created, or the virtual machine was added to the library during a library refresh. To correct this situation, deploy the virtual machine to a host by using a local area network (LAN) transfer, and then store the virtual machine in the same VMM library, library share, and logical unit number (LUN).

  • Migrate a virtual machine from one host to another

    Important

    If you migrate a virtual machine that is connected to SAN storage, the virtual machine will not be able to reconnect to the SAN unless the destination host also has access to that SAN. VMM is not able to detect if a virtual machine is connected to a SAN or if the destination host is connected to the same SAN, therefore cannot provide a warning. You must ensure that the new host is configured to allow the virtual machine to reconnect to the SAN before you migrate the virtual machine.

When you make a SAN transfer, the logical unit number (LUN) containing the virtual machine is remapped from the source computer to the destination computer instead of transferring the files over the network. Therefore, SAN transfers are much faster than standard network transfers and are independent of the size of the files being transferred.

If a properly configured SAN is available, VMM automatically uses the SAN to make transfers. However, if you use the Store Virtual Machine Wizard, Deploy Virtual Machine Wizard, or Migrate Virtual Machine Wizard to perform a transfer, you can override the SAN usage and make a local area network (LAN) transfer. For more information about how to configure a SAN for VMM, see the "Configuring a SAN Environment for VMM" topic (https://go.microsoft.com/fwlink/?LinkId=102218).

Designated Host for Virtual Machine Deletion on a SAN

When you create and deploy a virtual machine that can be transferred on a SAN, the virtual machine's files are stored on a logical unit number (LUN) of the SAN. This LUN is mapped and allocated to the host on which the virtual machine is deployed. VMM supports one volume per LUN and one virtual machine per volume.

When you delete a virtual machine that has its files stored on a LUN, the empty LUN remains mapped and allocated to the host from which the virtual machine was deleted. Over time, empty LUNs can build up and become spread out over a number of hosts, making it difficult for you to locate empty LUNs to use for creating new virtual machines.

One way to avoid this difficulty is to designate one host that you consistently use for deleting virtual machines. Before you delete a virtual machine, move it to the designated host. By doing this, you always know where to look for empty LUNs to create new virtual machines, which you can then migrate to other hosts.

See Also

Concepts

Planning for VMM Deployment
Planning for VMM Components and Features
Introducing Virtual Machine Manager