software equivs for netapps snapmirror / snapshots in FreeBSD fileserver ?

[Joe Schmoe]

I am very intrigued by some of the features that Network Appliance (NetApp) has for its network attached arrays.  Chiefly:
 
        snapmirror      http://www.netapp.com/products/filer/snapmirror.html
which allows real time replication of a filesystem(s) over a WAN - and saves bandwidth by transferring changes only.

        snapshot copies http://www.netapp.com/products/snapshot.html
which provides point-in-time snapshots of a filesystem(s) that can be returned to at any time - it keeps track of changes only (after the original snapshot data is created)
 
So ... if I want to use some features like this on my home fileserver (replicating to a friends fileserver over T1) ... do I have any hope of achieving these features with standard UNIX tools and scripts, or do I really need to buy things made by NetApp (or their competitors) to get features like this ?

		
---------------------------------
Do you Yahoo!?
Friends.  Fun. Try the all-new Yahoo! Messenger