VMware Paravirtual SCSI Controllers

About VMware Paravirtual SCSI Controllers

Paravirtual SCSI (PVSCSI) controllers are high performance storage controllers that can result in greater throughput and lower CPU use. PVSCSI controllers are best suited for environments, especially SAN environments, running I/O-intensive applications

PVSCSI controllers are available for virtual machines running hardware version 7 and later.

PVSCSI controllers have the following limitations:

  • Hot add or remove requires a bus rescan from within the guest operating system.
  • Disks on PVSCSI controllers might not experience performance gains if they have snapshots or if memory on the ESXi host is over committed.
  • If you upgrade your Linux virtual machine to an unsupported kernel, you might not be able to access data on the disks attached to a PVSCSI controller. To regain access to such disks, you can run vmware-configtools.pl with the kernel-version parameter to regain access.
    • Upgrade the guest kernel but do not restart the guest.
    • Run the VMware Tools configuration with the kernel-version parameter and pass the kernel version within the guest:

vmware-config-tools.pl –kernel-version kernel_version.

To determine the kernel version, search for the directory name that was created in /lib/modules during the kernel upgrade. Use that directory name, including all dashes, periods, and other characters as an argument to –kernel-version.

  • Restart the guest.
  • MSCS clusters are not supported.
  • PVSCSI controllers do not support boot disks, the disk that contains the system software, on Red Hat Linux 5 virtual machines.
  • clip_image002Prerequisites

    1. Verify that the virtual machine has a guest operating system with VMware Tools installed. Only for adding existing disk or creating new disk

    2. Verify that the virtual machine has hardware version 7 or later.

    3. To access boot disk devices attached to a PVSCSI controller, verify that the virtual machine has a Windows 2003 or Windows 2008 guest operating system.

    4. In some operating systems, before you change the controller type you need to create a virtual machine with an LSI Logic controller, install VMware Tools, then change to paravirtual mode.

    clip_image004 Procedure

    1. In the vSphere Client inventory, right-click the virtual machine and select Edit Settings.

    2. Click the Hardware tab and click Add.

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    4. Select a SCSI device in the Connection panel.

    5. Select an unused Virtual Device Node and click Next.

    For device node SCSI (0:2), 0 is the controller number and 2 is the number of the device that is attached to the controller. If you select a node on which devices already exist (for example, SCSI 0:3) you will add a SCSI device to the existing controller. To add a new controller, you must select an unused device node on an unused SCSI controller (for example 1:0).

     

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    1. Review your selections and click Finish.

    New SCSI Controller (adding) and New SCSI Device (adding) appear in the Hardware list.

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    1. Click OK to save your changes and exit the dialog box.

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    8. Reopen the Virtual Machine Properties Editor.

    9. Select the new SCSI controller and click Change Type.

    10. Select VMware Paravirtual and click OK.

    11. Click OK to save your changes and close the dialog box.

     

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