More explanation.

README.md

@@ -3,6 +3,10 @@ zfs_transfer
 
 Maintain a mirror of ZFS pools over the network.
 
+Best used together with https://github.com/zfsonlinux/zfs-auto-snapshot
+set up on the remote host. It should be possible to chain multiple ZFS
+hosts.
+
 Below is a crontab usage example. Here the various datasets
 and snapshots from the host 192.168.1.14 are replicated to our local
 ZFS pool, using SSH (-o Compression=no -c arcfour) and caching (mbuffer)
@@ -21,7 +25,13 @@ destroy the latest mutually known snapshot.
 The script should be quite tolerant against various failure conditions.
 If you can make it better, please do!
 
-- by jaakkos, on Fri Sep 5 2014
+In below crontab, the remote pool is called "backuppool", and the local site
+is "offsite".
+
+The "Keep days" parameter only destroys local (offsite) snapshots. It
+makes sure that a hold is released, if exists, on the remote host before
+it goes on to destroy a local snapshot. Failure to do so, would disturb
+snapshot expiry on the remote host indefinitely!
 
 ```
 MAILTO="user@host.com"