by February 22, 2006 0 comments

We have talked about OS virtualization many times in our
earlier issues. This series is a platform where we shall be discussing the
latest happenings in the realm of virtualization. We will also be looking at
various virtualization products available in the market. In this first part, we
take up some hidden features of the VMWare Workstation and see how to make the
best use of this product.

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OS cloning       
Installing and configuring many copies of the same OS, along with
applications on machines is time consuming. To save time, there is a feature to
clone systems in VMWare. This makes copies of a virtual machine. To create
clones of an OS running in your virtual machine, first select that machine from
the list on your VMWare Workstation screen and then open the ‘Clone Virtual
Machine Wizard’ and click on Next. Select the state of the parent to clone and
go to the next step. On the subsequent screen select the type of clone you want
to create. Here you have two options: ‘Full clone’ and ‘Linked clone’. A
full clone is an independent copy of the virtual machine and 
will share nothing with the parent virtual machine. The linked clone will
only share the VM definition, while sharing the same virtual disk image. With
linked clones, you save on disk space, but changes in one will affect all the
clones. Full clones, on the other hand, will use up a lot of disk space, but
each copy after the cloning process will remain unique. Select the type of clone
and click on Next. Now, you need to fill in a name for the clone and the path to
save its files to. Enter them and click on Finish. It will take a few minutes
while the cloning process completes. Note: You will need to switch off the power
of the parent virtual machine during the cloning process.

Create a virtual computer lab inside a VM using teams. It creates virtual LAN segments and adds virtual machines in that LAN segment

Improve performance
Virtual machines run too slow on the host OS even when you assign it
a lot of RAM. This loss of performance is due to memory utilization issues in
the host OS. If we could minimize how much memory the host OS uses up, the VM
can run faster. To achieve this, you need to:

  • Defrag your physical disks before
    you install a VM and then regularly after that. This prevents fragmentation
    of the virtual disk image file as well.

  • Generally when you create a
    virtual disk in VMWare Workstation, it creates a dynamic disk that resizes
    according to how much data you put in it. This again leads to disk
    fragmentation. Our suggestion is to create a separate physical partition for
    your VM disk images. Also, when you add VMs, use the ‘Allocate all disk
    space now’ option to make a fixed size image.

  • If you are using an anti-virus on
    your host system, it would have a ‘real-time protection’ feature. This
    monitors I/O operations and performance is lost because of this. To avoid
    this, you need to set up an exclusion filter for VMDK files in the

  • When you use VMWare, you have to
    define the amount of virtual memory for each VM. At runtime, VMWare frees up
    unused VM memories and returns it to the host OS. This allows you to run
    multiple virtual machines simultaneously.
    However, every time a guest OS demands more memory from the host, it slows
    down that virtual machine dramatically. To overcome this problem, open the
    virtual machine’s VMX file in the Notepad and add the line
    ‘MemTrimRate=0’ in it.

  • VMWare uses page-sharing to
    provide guest memory pages with the same content to be stored as a single
    copy-on-write page. This technique decreases host memory usage, which in
    turn affects system resource usage, including I/O bandwidth. 
    To avoid this overhead for the guest OS when sufficient physical
    memory is available, you can disable page sharing by adding the line
    ‘sched.mem.pshare.enable=FALSE option’ to the VMX file.

LAN teaming
VMWare Workstation allows you to setup a virtual computer lab with
its ‘teaming’ feature. You can make a virtual network between multiple
running VMs. This helps you network the VMs and also create private virtual LANs
for the team members to communicate securely. The virtual LAN segments are
completely independent and invisible to the host OS/network. You can also use
this feature to create DMZ to securely bridge between team members from the
outside network. To create teams, select File>New>Team. This will launch a
wizard. Click on Next and then type the name and path to save the team
configuration files, and again click on Next. You need to add virtual machines
to the team and then select the ‘Yes’ option before going to the next step.
Click the ‘Add’ button on the screen to add machines. Add your existing
virtual machines and continue to the next screen. To specify the LAN segment for
the virtual machines, select the ‘Yes’ option and go to the screen after
that. Before the final step, you will be shown each VM and its LAN segment.
Click on Finish to complete the wizard.

Install Solaris 10
VMWare Workstation 5 did not support running Solaris as a guest OS.
But, with the 5.5 version, you can install both the 32- and 64-bit editions of
Solaris 10 as a guest OS. However, before proceeding to install Solaris, you
need to prepare your system appropriately.

When you use the wizard to create a virtual machine, it
takes the default settings—we need to change some of these for Solaris.
Firstly, on the virtual disk screen, change the size of the disk to 10 GB. The
LAN settings should be modified to the ‘Bridge Mode’ option.

Once you have configured the virtual machine as above,
insert the Solaris DVD and boot the VM off the DVD. 
Use the full installation option to install. We have detailed the
installation process in the article Solaris 10: Installing the OS, PCQuest,
September 2005. Now Solaris should work fine in your VM.

Sanjay Majumder

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