Cytrix removed auto start from the easy to access options using XenCenter for 6.X servers.

However you can still run it.

First enable it on your pool

• xe pool-param-set uuid=UUID other-config:auto_poweron=true

Then run a command to get all of the VMs in your pool and turn auto power on for all of the VMs that are currently on.

• xe vm-list power-state=running |awk -F: ‘/uuid/ {print “xe vm-param-set uuid=”$NF” other-config:auto_power=true;”}’

This will give you a list of commands to enable auto_poweron for each of the running vm in your pool