CarbonCopy as posted is the only way to gain more control over your backups...Time machine has a set way of doing things, and fussing with it isn't really a good idea...you can of course exclude large files, folders and drives. I have a Pegasus R4 which I use to copy mission critical data to...two RAID0 arrays, one for archival purposes and the other takes care of current work. My TC backs up my Imac and my MBA.