TOPIC:

Glad you got it working. Regarding switching the slave/master roles, you can try to designate a new master, but, while the transition occurs, there will be no disk access since we will be demoting the former master and promoting the new master to host access to the disks. If it is not absolutely necessary, I would caution aginst it in a live pool. If the xe commands dont work, you can also try mmoving all VMs to the slave and then reboot the master.

Up to this moment I did server reboot to change master because wasn't sure if changing pool master will also change primary DRBD and ISCSI Target.
Now I have one mo question. With HA enabled VM starts automatically after VM shutdown. I have an APC UPC and want to do automatic VM and server shutdown in case of power outage. What is the best way to do this? Because if I will make a script to shutdown VM, I think it will begin to start before I shutdown the Xenserver. So the solution which came to my mind would be first disable HA, then shutdown VM and then shutdown Xenserver. When Xenserver will start automatically after electricity restore the startup script will enable HA and start all VMs.

Disabling HA with your script will stop the VMs from starting again. - add "service ha-lizard stop -w" to your script. Make sure to include the '-w' which also stops a watchdog service otherwise HA will restart itself.