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Using P2V to Enhance DR Operations

Disaster recovery has traditionally been one of the most popular use cases for virtualization. Now the idea of physical-to-virtual conversion for DR is getting some traction. I agree this is a good idea, and in fact many of our customers use this approach.

First, here's a quick overview of the basic process and requirements:

  • The organization needs to have a hypervisor in place to accommodate the physical server after it is virtualized.
  • Using physical-to-virtual (P2V) conversion software, a virtual version of the physical server is created.

Once the VM is created, there are several options. Here are two of them:

Option 1: You can replicate the VM to the DR site using an image-based replication tool (if you want to replicate, I recommend replicating the image using a solution designed for image-based replication, or backing up the replicate of the physical host locally and replicating the image -- see my post on WAN backup for an explanation).

Option 2: You can create a backup image of the VM. The backup image can be stored locally or transferred to a DR site. Using the backup image, the server can be restored either as a VM, or as physical system using virtual-to-physical (V2P) software.

Now, here are a few things you should know about using P2V for disasters recovery.

What RTO benefits do you get from these options?
For starters, by simply keeping an image of your physical host up to date on your hypervisor you can just power it on in the event of a failure. This is a less-than-5-minute-RTO on your hypervisor -- a big advantage versus rebuilding the physical host from the ground up on hardware you may or may not have.

If you're replicating the physical host copy from the LAN to the WAN you get the above benefit for the LAN, and the DR site benefit of having an off-site image you can power up for a quick RTO.

What about RPO?
Most P2V software solutions will keep an image up to date either with a full copy, or with incremental updates, so your RPO is of the last successful P2V cycle. If you're backing up this physical host copy on a regular basis you then have a regular RPO you can restore to on your hypervisor. This still will be faster than rebuilding the physical host from the ground up on hardware that may not be immediately available after the disaster.

Is there something for onsite RPO and off site RPO?
Yes. If you're replicating the backup archive of your physical host, copy to a device in the LAN that can then replicate the archive off-site to another device, you now have a regular RPO for the LAN site and the DR site.

What makes this approach work?
Fast, easy-to-use P2V conversion software is the key for successfully using virtualization to protect physical servers for DR. If you can conveniently convert your physical servers to VMs, virtualization has many benefits for DR. One of the biggest is comprehensive recovery. When working from an image-based backup file, you won't have to rebuild the server before restoring data to it. The image includes all the settings, applications and data you need to have the server back up and running in minutes.

VMs do not need to be restored to the same physical hardware they were backed up from. This can be a big money saver, because organizations can use older equipment at their DR site, rather than duplicating their primary infrastructure there. A related benefit is flexibility -- you can recover any system to any location.

P2V conversion and the resulting backup can boost the recovery performance of your disaster recovery plan. I encourage you to investigate whether P2V conversion is a good option for your physical servers.

Posted by Jason Mattox on 12/29/2010 at 12:49 PM


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