server configuration

Hi All,
It has been a while since I used proxmox (more than 3 years, nice to see the progress.....
I'm about to install two servers next week and have some questions:
First, server config is like this : one server with raid-1 and 1.5T and 2X 240G SSD drive, the other server will have only 2X120G SSD.
The 1.5T hard drive will be mainly for file backup, not for VM.
Live migration, after making a lot of reading I'm not sure if live migration of CT is working out of the box or that I need to install some other utilities.
What will be the best choice for the partitions (LVM2/ext4, I'm using SSD and I understood that for SSD ext4 is better).
With this kind of setup, what will be the best option to achieve HA or at least to have a minimum down time if one server crashes?

Thanks.