TOPIC:

Hello, I've used HA-Lizard on two empty XenServer 6.5 boxes and it worked successfully. However, it was almost a year ago so I forget the exact steps taken. I was wondering if it is possible to do the installation while one server has virtual machines installed, while the other server is brand new and does not.

So, prior to DRBD sync does the volumes have to be formatted, or is it possible for the data on server 'A' to be replicated to server 'B'?

Technically speaking, this is possible, but not recommended.
If you choose to try it, do not use the automated installer. Following the reference design guide is your only choice, paying careful attention to the initialization of the DRBD storage. You may need to change the method we use, which is to store metadata on the disk. Since you are starting with a disk that has data on it already, storing DRBD metadata on the disk could result in a loss of data.

You may want to consider exporting all of your VMs to a safe place and then importing into a new cluster.

I understand, thank you for your reply. Now that I'm fresh on the process again, I understand why it wouldn't work, I forgot about the DRBD metadata being stored on the disk.

I found it was easier for me to move the VMs on a temporary USB SR, do the noSAN process, then move the VMs back. I was not able to do a live migration for whatever reason though and had to shutdown and detach the disk from the VM. (Dell R630, Intel Broadwell Xeon CPU)