6.1.2-15132 Update from 6.1.1-15101 failed on ESXi Server as several discovered already.
Therefore, I did the following to bring it up & running:
I did a fresh install in a new directory on the ESXi server with an 8GB virtual disk.
6.1.2-15132 installs without any issues.
I shut down the virual machine and moved the second virtual disk (4TB) from the 6.1.1-15101 installation to the new 6.1.2 installation directory.
Then in VM settings I added this existing virtual disk with all my data to the newly created virtual machine.
After restart, DSM reported an error on the new volume and offered to repair it (my guess, it copied the 200MB DSM files from the 8GB virtual disk one to the 4TB virtual disk two, as they were not the same).
I started the repair routine wich ended up with an okay.
After a reboot, everything was up and running, all data on my big virtual disk were there.
So, for me it worked, hovewer:
Don't forget, Jun's 1.02a loader is in alpha status.
If you are testing things as I explained above, make shure you have a good backup concept. That it worked for me on my ESXi server does not mean, it works at your's as well.
So be cautious and backup your valuable data before experimentig ...
Good luck