We've been through the ringer with data loss and hard drive failures. What we have is an expensive solution, but it was designed to grow with us.

We built a Linux-based media server running two 2TB (2000 gig) hardware RAID-5 arrays (4 - 750gig drives in one, 3- 750 gig drives in the other, with one hot spare.) These arrays hold all of the edited AVI (full res) and WMV (web-encoded) videos as well as stills and screencaps. If a drive in either array were to fail, the hot spare would kick in and rebuild the array without any user interaction from us, then we'd just have to replace the bad drive. This media server cost us about $3,000 to build, but it's fast enough that we can edit and render directly to and from the media server.

Then, for secondary backup, all the stills are stored on a Terastation software-based RAID-5 1TB box.

We also have an SDLT tape backup that will (soon) have a complete backup of the entire media server, and all of our unedited HD video content is also stored on SDLT, since it's too large to fit on any other media or to keep online (roughly 1.5 gigs/minute of video.) Edited HD video is stored on the media server. The backup tapes will have two sets offsite and one onsite.

We spent a fortune doing all this, but our content is our lifeblood, and so we considered it to be a reasonable investment for our security.