What is VMware vCenter Converter?

VMware vCenter Converter Standalone provides an easy-to-use solution that automates the process of creating VMware virtual machines from physical machines (running Windows and Linux) and from other virtual machine formats.

For more details, see the following link to the VMware product documentation:  Link

Recent Use Case:

While working on a major VMware upgrade for a recent customer, one of the tasks I had was to remove the reliance on aging iSCSI volumes configured directly inside the virtual machines operating system.

This was part of a larger piece of work where I was replacing 2 SANs and 8 hosts so the old iSCSI volumes had to be dealt with too.

I chose to tackle this using the vCenter Converter as it allows hot conversion, this enables the newly converted machine to have converted disks which appear as VMDKs on the new storage rather than iSCSI volumes on the old storage.

First few migrations went without a hitch – excellent!

The problem:

Next up was a large file server consisting of millions of files with terabytes of data across multiple disks/volumes, I knew this would take some time but since my initial review and the actual time of completion one of the drives had become close to capacity (200mb free of 2TB).

I configured the conversion job and ideally wanted to maintain the disk sizes. After around 30 hours the job failed with this message:

Not ideal because of the length of time it took to fail.

I started looking in the documentation for answers on how to deal with this when the volume referenced was the one that was almost full (There was no option to remove some data to free up space).

What I had overlooked was the problem was not on the source machine but actually on the converted machine, the worker service requires so much space on the destination, by default this is 10% of the capacity.

The resolution:

After reading through VMware article: KB2148918 I made the changes recommended.

• Navigate to: C:\ProgramData\VMware\VMware vCenter Converter Standalone\
• Edit the converter-worker.xml
• Change the value from 10 to 0: <minVolumeSizeExtraPercentage>0</minVolumeSizeExtraPercentage>
• Restart the VMware vCenter Converter Standalone Worker service

I recreated and started the conversion task and this time the conversion was successful.

Note:

When using the advanced disk configuration options, the option to “maintain size” or change the disk size will incur different behaviour during the clone operation. If you use “maintain size” you will get a much faster block level copy. If you adjust the disk size then be prepared to wait much longer as you will be forced into a file level copy operation.