Hi Geert,
the eventlog is written to the file /mnt/harddisk/log/messages on the VCS.
The messages log file (Along with various other log files) is rotated once it reaches around 10 megabytes in size, so that messages becomes messages.1 and a new messages file is created.
Further, the previous messages.1 is rotated to messages.2 and so on, and the VCS holds up to 200 rotations for most or all of the various log files.
Hope this helps,
Andreas