User guide

What is the machine's processing power?

Conversion will take the selected machine's CPU resource. Multiple conversion tasks will be queued

on that machine and it may take considerable time to complete them all. Consider this when creating

a centralized backup plan with conversion for multiple machines or multiple local backup plans using

the same machine for conversion.

What storage will be used for the virtual machines?

Network usage

As opposed to ordinary backups (TIB files), virtual machine files are transferred uncompressed

through the network. Therefore, using a SAN or a storage local to the machine that performs

conversion is the best choice from the network usage standpoint. A local disk is not an option

though, if the conversion is performed by the same machine that is backed up. Using a NAS also

makes good sense.

Storage space

Disks of the resulting virtual machine will use as much storage space as the original data occupies.

Assuming that the original disk size is 100 GB and the disk stores 10 GB of data, the corresponding

virtual disk will occupy about 10 GB. VMware calls this format "thin provisioning", Microsoft uses the

"dynamically expanding disk" term.

Since the space is not pre-allocated, the physical storage is expected to have sufficient free space for

the virtual disks to increase in size.

4.6.3 How regular conversion to VM works

The way the repeated conversions work depends on where you choose to create the virtual machine.

 If you choose to save the virtual machine as a set of files: each conversion re-creates the virtual

machine from scratch.

 If you choose to create the virtual machine on a virtualization server: when converting an

incremental or differential backup, the software updates the existing virtual machine instead of

re-creating it. Such conversion is normally faster. It saves network traffic and CPU resource of the

host that performs the conversion. If updating the virtual machine is not possible, the software

re-creates it from scratch.

The following is a detailed description of both cases.

If you choose to save the virtual machine as a set of files

As a result of the first conversion, a new virtual machine will be created. Every subsequent

conversion will re-create this machine from scratch. First, a new (temporary) virtual machine is

created. If this operation succeeds, the old machine is replaced. If an error occurs during creation of

the temporary machine, the temporary machine is deleted. This way, the conversion always ends up

with a single machine. However, extra storage space is required during conversion to store the

temporary machine.

If you choose to create the virtual machine on a virtualization server

The first conversion creates a new virtual machine. Any subsequent conversion works as follows:

 If there has been a full backup since the last conversion, the virtual machine is re-created from

scratch. This involves creating a temporary virtual machine, as described earlier in this section.