More Bang for your Buck with PVSCSI (Part 2)

Part 2 Doing the work

As you might have noticed, this blog post is a continuation to my first post about PVSCSI, you can access Part 1 here.

Hopefully now you have a better understanding of what the Paravirtual SCSI driver is all about, and we can prove there are tangible reasons to move in this direction.  Let’s get on with the important part, the implementation phase.

SCSI2

(I need to finish off this blog post, I am running out of pictures of SCSI cables)

There are some caveats I need to start out with.  In case you missed it, PVSCSI drivers on virtual machines aren’t supported on operating system disks unless you are running vSphere 4 update 1.  You can use the driver on a secondary data disk if you so desire, but for this post I am going to assume you are running vSphere 4 update 1 (Virtual Center and ESX Hosts) and want to know how to get the driver working on all disks.

In most cases, it’s always easier to build new.  You know you have a clean install, the drivers are updated, the configuration is solid.  I would suggest updating your templates to include the new paravirtual scsi driver.  Your existing virtual machines run fine with their existing configurations, and depending on your environment, it might be a lot of work to go back and target all of your virtual machines.  For an upgrade path, my personal opinion would be to target your heavy I/O virtual machines.  Upgrade the VM’s that will make a difference, and you will see some immediate benefits.  Reducing the I/O on the disk subsystem will only benefit the other virtual machines that might share those same physical disk spindles.

Clean install

This section will walk you through the process of installing the driver with a Microsoft Windows 2003/2008 operating system.  Currently these two operating systems are the only ones supported.  Hopefully we will see some added support for the various Linux operating systems down the road.

Walk through the “New virtual machine Wizard” as you normally would.  On step 9, ensure you select the “VMware Paravirtual” option as seen below.

para_wiz

Before powering your new VM up, you need to connect the virtual floppy image file that has the driver for your desired guest operating system.  This is not on the VMware.com website under downloads, it already exists on your ESX host.  You will need to browse to the following location on your ESX host. [Datastores]\vmimages\floppies I would wait to connect your floppy disk image after you boot off the Windows CD-ROM so it doesn’t try to boot off the floppy drive.

pvscsi-flop

When you power up your new virtual machine, select the F6 option to tell the operating system you need to use a third party SCSI driver:

windowsf6

Now connect your floppy disk image to your virtual machine under the “edit settings” option.  You should now be able to point to operating system to the driver as seen below:

pvscsi_select

Continue on with your normal installation, and you are complete.  Your new virtual machine is now utilizing the Paravirtual SCSI drivers.  I suggest now converting this image you created to a template for future deployments with this configuration.

Upgrading and Existing Virtual Machine

To upgrade an existing virtual machine, the process is pretty straight forward.  Assuming you have already upgraded to the latest virtual hardware (Version 7), make sure your VMtools are upgraded post Update 1.  Shut down the VM, and edit the settings “Change Type” as shown below:

chng1-pvscsi

You will get another window that will alllow you to change the type of controller as seen below:

chng2-pvscsi

Select the “VMware Paravirtual” and then select ok.  Boot up your virtual machine and you are all set.  Your system is now running with the updated drivers and you can take advantage of the newer drivers that provide better throughput and less latency!

Hope you found this post useful.  Good luck!

Scott

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  • Mihir

    good articles, thx! 🙂 i couldn't find vmimages in the hosts' datastores. we upgraded from esx 3.5.0 U2 to 4.0 U1. the only directory i see is 'esxconsole…'. any ideas?

  • Rlwagner

    Same question I cannot find the pvscsi floppy files.

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