Planning Data Protection Into Your Virtual Infrastructure - Page 1

Sep 11, 2008

Brian Gardner

As an IT manager within a small or medium-sized business, you've read of all the advantages that come with virtualization. The next step is to feel comfortable tackling a migration to virtual infrastructure and to make sure it is protected.

To begin, it is important to understand the things you need to do to plan a virtual infrastructure and choose the appropriate data protection for it. Identifying and selecting the capabilities and limitations of data protection within your virtual infrastructure is one of the most critical tasks.

For simplification, this article limits the virtualization platform example to VMware ESX. The process is the same for Microsoft Hyper-V, Virtual Iron and others until you get to the end and have to determine the right implementation.

What applications should I virtualize?

With current virtualization technology almost all applications can be virtualized. You just have to decide on a reasonable set of applications and then compile the following information:

  • 1) Identify characteristics of selected apps under load

    It is absolutely critical that you characterize these applications under their heaviest expected load or you'll start running out of resources unexpectedly when you implement your virtual infrastructure.

    Total memory footprint
    Memory the application uses at peak load? If the application "leaks" memory (its memory footprint grows even under constant load) you'll need to allow room for that as well.

    Total CPU utilization
    How many CPUs and at what percentage used at peak load? Don't forget to note the type of CPU you used when you did your measurements.

    Total disk space including growth to next budget cycle

    Network bandwidth utilization
    Network bandwidth used by this application at peak load. Remember to account for both directions of network traffic.

    Storage network throughput (SCSI, FC, iSCSI, NAS) as both input and output
    The same thing you just did for your messaging network.

    Disk reads and writes
    The disk activity that this application requires at load. There are other disk load parameters that may need to be characterized as well, depending on the application.

    Memory bus utilization estimate (memory bus available bandwidth minus four times the total I/O)
    Years of empirical data have upheld this useful rule of thumb. This can be somewhat difficult to get since it is not always easy to identify the memory bus speed of a particular system.

  • 2) Identify load patterns and recovery requirements for virtualized applications

    Is there a window during the day or night when they could reasonably be shut down and backed up?

    Is there a window during the day or night when the total load on the ESX physical server is low enough that backups can be performed without negatively impacting the running apps? If there is no application and ESX server available window, you will need to select a proxy backup method.

    Do you need to be able to recover individual files on a regular basis? If so, you will most likely need to run a backup agent directly within a virtual machine.

    If you've designed and implemented a few data protection architectures, the requirements gathering process was probably quite familiar to you. It doesn't change much for virtual infrastructures.

    Once you understand your application and data protection requirements there are some simple decisions to make:

    Agents in each virtual machine

    This is the simplest decision, since it mirrors what you are already doing with your physical infrastructure. The strengths of this approach:

  • Low disruption to existing workflows
  • Easy application backup and recover
  • File level recovery

    There are two significant weaknesses to this approach:

  • Total cost of backup software agents
  • Need to manage load on ESX server when running backups

    Agent in Hypervisor Service Console

    This is pretty simple as well. It only requires a single Red Hat Linux agent for each ESX server.


  • Low agent cost
  • High performance image backup & recovery (only working with vmdk files)


  • Need for some scripting
  • Lack of file level recovery
  • Lack of application awareness
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