I have a 750G drive as my boot drive. I have not yet picked up a descent Time Machine drive yet so I just threw a spare 320 in there to hold me. Time Machine worked great and I could go back several months. All was well and good until the other day. My main drive has now reached about 320 gigs. So my Time Machine backup is pretty much a 1-to-1 copy. So I can only go back about a day. This is not good. Now is the time to buy a bigger drive. Here lies the problem. If I go for another 750, eventually I will run into the 1-to-1 copy problem. If I buy a 1TB drive then OK, but eventually when my 750 fills up, the 1TB isn't going to be much good since it will probably only give me a few days worth of backups. The rule of thumb was supposed to be that your Time Machine drive be at least twice the size as the drive it is backing up. (Don't know if that's an Apple thing, or just something the community agreed on. Probably the latter.) It would be nice to have a 750G drive as my main drive and 2x1TB of Time Machine backup space. But Time Machine does not let you span drives. So what are you supposed to use if you have a 1TB hard drive that is full? Time Machine becomes kind of useless if it's a 1-to-1 copy. The whole point is that you can go back in time and retrieve a lost file. So ideally, keeping at least 1 month would be nice. I mean, how long is it before you realized you lost something? Anyone have any tips, tricks, or RAID solutions? Comments?