Hi maof2, here's my thoughts on your last post.
I think what the Cameras King IP Cam guy told you about losing the whole recording is incorrect. The IP cameras record files in short intervals. For the Dlink cameras, its something between 1-3 mins per file. So something goes wrong, you'll lose that bit of the recording. All previous recording should still be fine. And I'm surprised if he said it applies to "normal" IP cam. Does that mean his solution is "special"?
Unfortunately, the Dlink cameras I have do not have IR functions. A pity, true, but for what I'm using it for, ie monitoring the home while away and not catching burglars, it's still ok for me since I'm at home at night. And the DCS-2121 also allows you to download the videos over the network, without needing to take out the card.
As for Jessica's solution, only comment I'd like to make is if you are looking at 3 cameras, you probably need to take the cost of 1 at $30, and th other 2 at $90 ($60 for a pair of adapters, and $30 for the camera). But it is cheaper that an IP cam solution, assuming there's no installation cost. As you pointed out in your findings at Sim Lim, cabling can be costly (PVC casing, manpower, etc). I'd be pleasantly surprised if installation comes free.
As for your question to me, I use a Network Attached Storage (NAS) device, not a Storage Area Network (SAN). Close, but very different. There are many resources on the internet on NAS. Below are some you can start with:
http://en.wikipedia.org/wiki/Network-attached_storage
http://compnetworking.about.com/od/itinformationtechnology/l/aa070101a.htm
If you want to see a sample set up guide, you may find the DLINK one a good starting point.
http://global.dlink.com.sg/site_support/DNS-323/Manual/DNS-323_B1_Manual_v1.3.pdf
But do note that NAS is not cheap. So if you are on a tight budget, it may not the most appropriate solution for you. FYI, the DLINK NAS without the disk already cost about $270.
Hope this helps.