hda - (the 1.4 gig primary drive)
hda1 - /var reiserfs rest of the space
hda2 -128 MB ext3 /boot partition
hda3 - 1/2 of your total swap
hdb (the 4 gig)
hdb 1 - 2 gig reiserfs /
hdb2 - other half of total swap
hdb 3 - /opt reiserfs about 1 gig
hdb 4 - /<wherever you will keep config files backed up> reiserfs about 1 gig
depending on your logging (how much and how long you keep them) you may want to switch hdb1 and hda2 to give /var some more space. Just be sure to keep /var close to the beginning of the drive for better performance, as writing log files will be what the machine does most often.
The separate partitions for /opt and your config backups are merely for convenience, in case you have to ever reinstall. Personally, I'd forget about /opt and enlarge / for a gateway/DNS machine, but your needs may vary.
For security, don't mount /boot , and lock the whole machine down tight. Go back and open only the ports you need, one at a time. Look into your needs and determine which, if any, partitions can be mounted nosuid/noexec. Then be prepared for hundreds of hits per day on your ssh server
Others here are more qualified to tell you how to lock down your services, and I'm sure they will chime in.