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Virtual recovery… to the rescue (Part 4)

In order to provide fault-tolerance across any IP network (LAN or WAN), back-up solutions should be able to replicate the bytes of data that change to another windows server somewhere in the enterprise. There are a number of ways of combining the technology to achieve these outcomes:

1. Installed within the guest OS, it enables replications on any part of the files or directories within the virtual machine disks, while the target server has no idea that the source server is a virtual machine and not ‘real hardware’. Upon failover, the target server would assume the name, IP, shares and services of the failed guest OS.

2. The most common solution is, however, installation on the host OS to maintain replicas of all the virtual disk files on the target server. The target server would monitor the guest OS for failure, but instead of assuming its properties it would simply invoke a script that would initialise the virtual server on the target server. The virtual server would then use the replicated virtual disk files that hold the actual configuration and data from the guest OS.

3. Alternatively, while the guest OS system partition is a virtual disk, the actual data drives may be allocated partitions of the host OS. In this case, the back-up would be installed on the host OS of the source platform and replicate both data from the allocated partitions as well as any virtual disk files being used by the guest OS(s).

In the event of a failure on the source machine, the target server would invoke the virtual server on the target. Once this server starts, the virtual machine could be started using the replicated virtual disk file(s) and data replicated from the allocated partitions on the source server.

As the target server might be used for the failover of multiple servers, care would have to be taken to prevent compatibility issues. During failover, the target server would need to be configured to start virtual machines corresponding to each source server.

Protecting multiple production applications (or clients) using one disaster recovery server is possible through a combination of real-time data replication with virtual infrastructure architecture. These technologies combine to offer leading-edge disaster recovery solutions, with proven flexibility to deliver enterprise-class protection anytime, anyplace, anywhere.