Size of the XML itself? That is going to vary based on what you have configured, total lines of code, and # of appliances you may/may not have in cluster.
M680, based on SMA as stand-alone, should be similar --- you are probably looking @ < 1 MB...
Looking @ my test environment, in which I have a nightly cron job set to grab a backup of...
-rw-rw---- 1 robert robert 161115 Sep 26 02:00 C000V-564D1A718795ACFEXXXX-YYYYBAD60A5A-20140926T020002.xml
So, 161115 bytes = .15 MB
-Robert
