There are many articles on this topic - just try VMware or Xen website. Here's the basic foundation - backup is an I/O intensive process. Virutalized server environments consolidate servers to maximize CPU utilization, but guess what you now have more machines sharing the same I/O path whether it be through the processor, the network card, or storage. Traditional streaming backup approaches - a client on the server - do not work well in virtual environments because they slow down all of the other guests by using up I/O resources. You can back up the machine this way, but it requires scheduling when other machines are dormant. Client-side deduplication agents from the likes of Symantec PureDisk and EMC Avamar can improve this process by eliminating redundant data before sending anything over the network.
Storage level snapshots can provide an alternate approach to backup of virtualized servers, but this will be an image-based backup of the full machine. So no granular file recovery and you run the risk of not capturing all files because some are open. That said I have heard from 1 NetApp user who claims to have no problem with VMware ESX snapshots using NetApp Snapshot provider.
<This post below seems to have nothing to do with backup in a virtualized environment. NetApp snapshots have been around for quite some time.>
Like many organizations, BT’s backup system for its X86 infrastructure servers had grown like Topsy. Some backups were taking 96 hours. Recovery was taking days to accomplish.
The architecture that BT took into place utilized storage virtual snaps, based on NetApp’s virtual architecture. This approach is not suitable for all applications, but very suitable for the majority of infrastructure systems (e.g. Web support systems). This allows multiple snaps to be taken during the day, and for recovery to bed one from those snaps. Backup is then done to a remote site overnight over BT lines. After 90 days the backup data is deleted. For applications that require data to be held after this, specific procedures for keeping the data longer are made. For Oracle and SQL database application that require a higher level of consistency, there is specific backup software available with NetApp.
Action Item: There are as many ways of skinning a cat as there are ways of providing backup and recovery. What is important is that the opportunity is taken to re-architect the backup system to be in line with the workload requirements.