Creating Large, Safe, and Cheap Network Attached Servers?

davco9200 asks: "I am looking to create a large data server for all my digital media files. The usage is the 'pro-user' category, to use the media from multiple stations in my house and at work. I value space (150+ gb would be nice), accessible from multiple platforms (Win, Mac), but perhaps most of all, some security (e.g. RAID 0 doesn't cut it). Total write or read access isn't that high of a priority. I have looked at things like the Snap 4100 that offer 160 gb or 300 gb and good raid options but the price seems high ($2,700 and $4,500 respectively). Has anyone had any experience making their own low-end NAS? Has anyone looked at the Adaptec IDE RAID Controller? This seems like a reasonable way of getting data parity so if one drive goes down your entire collection isn't lost. I figured Slashdot readers would have some good solutions. Information on specific cases, drives, and other pertinent facts would be helpful."