Virtualisation for Disaster Recovery

Hi,

Can anyone give me any ideas/links so that I can better get an idea of how virtualisation can help me from a disaster recovery point of view?

We have a server sitting in a datacentre, it basically has a has a bunch of web services that sit on the internet and a big SQL Server database.

I'm not looking for anything massively detailed, just something to give me an idea of what's possible.

Many thanks

From serverfault Geoff Wray

• There are all manner of product-specific answers to this question but the most basic and easy explanation is that a physical server's identity/code/data/etc. are all kept on the disks plugged into the server itself whilst a virtual server's disks are actually just a big flat file on a disk.

  And if you can put this flat file onto a shared disk system and then replicate that file to another shared disk system at a second site then you have an identical copy of everything that makes up that virtual server but somewhere else, somewhere it can be restarted and carry on as though nothing has happened.

  As I say there's lots of specific products to automate this or make it easier but essentially it's easier because your servers are just files - does that help? come back if you have any more questions.

  Geoff Wray : Thanks for the feedback it's very useful to get an idea of what can be done. Do you think there would be any performance issues running as a virtual server?

  Chopper3 : well yes, there's usually a 5-10% virtualisation overhead (more for IO intensive VMs such as DBs usually) but often people virtualise onto newer hardware so usually see and *increase* in performance over their older servers - but yes, on a like for like basis it'll be slightly slower.

  Geoff Wray : Thanks for the info
  From Chopper3

• Here's an example: Our company web sites are hosted externally. As a result of issues with our previous host, which resulted in several days of down time, I now keep a replica of those sites on two machines. One is used for development and testing, so can at times vary from the live site a bit. The other is maintained as an exact replica. This second one is normally only powered up as required for re-replication.

  In the event of issues with the web host the machine with the exact replica can be powered up and brought online via a change to the DNS record. As we are a small company there's no way I could justify the expense of an extra server to cover the pretty small chance of it ever being required. Instead I use a virtual machine. It's not as powerful as I'd like but it is perfectly workable.

  From John Gardeniers