How do I have two identical FreeNAS machines on a network?

[kss18]

I am in the process of setting up two HP n54l microservers as FreeNAS servers. These are going to be in physically different locations, but on the same subnet (bridged LAN). Each machine has 4 2TB disks, three in a mirror and 1 spare.

What is the best way to ensure that the data on both machines are identical? Is rsync the way to go or somethingelse? How do I mirror the machines themselves? Thanks.

 

[cyberjock]

ZFS snapshots is the best for that quantity of data.

HA is another, but that's not offered in FreeNAS.

 

[kss18]

Forgot to mention, most of the disk is empty -- the data is much less than 2TB -- a very large number of small flat files. To keep things simple until I graduate from noob school, I ended up installing btsync plugin, which seems to be working beautifully. Thanks for your help.