If you can access the web interface, then:
1. make a backup of your profile (logs excluded).
2. create new partition ext3 in the space that is available (assuming this is hard disk, you have tens of gigs free space).
3. restore profile to newly created big partition.
4. activate new profile.
done!
Now you have lotsa free space. If needed, you can configure some log rotation:
“Delete the oldest logs”
“Compress the oldest logs”