> Would it be possible to use for example a ZIP-Drive as storage for the 
> data as well (of course not for the Soekris box but for "normal" 
> systems)? The ZIP-Drive is slow but it can hold around 100MB of data.

hi Jürgen,

i would think any filesystem/device FreeBSD could mount could work. this little
bit of code in the statistics gathering script is what copies the database
off to permanent media:
if [ $mins -eq 30 ]; then
/sbin/umount -f /cf
/sbin/mount -w -o noatime /cf
cp /var/net4801.rrd /cf
/sbin/umount -f /cf
/sbin/mount -r /cf
fi

you'd just change that part to mount and copy to some other device.

note that the 100MB capacity doesn't make any difference in the particular
round robin database we've setup - our database is 1MB in size the moment it is
created, and remains 1MB in size as records are added every minute, day by day,
on and on. that is the nature of the round robin database. you can read more
about RRDTool here: http://www.rrdtool.com/

best,
jay w.