EXACTLY what I recommend (and do myself)
Just remember thare are several things you are protecting other than simple "Data"
as there are catagories of "data"
First your Data itself the actual files, and it doesn't matter is you are protecting text documents, pictures, Audio or video, this is simple "data"
that must always be protected and could be used in another system.
the next thing is your "system setup" all the little adjustments you make to your own preferences.
And the system itself so you don't have to call and whine at microsoft if/when your attempts to reinstall the system on your computer after your system/boot drive fails... and your system hard drive WILL fail.... More on that.... If you have never had your system drive fail either it is about to
(to teach you an important lesson) OR you have been sufficiently paranoid and swapped out your system drive for a "clone" and "derated" the previous drive from system use.
Personally I will use a HDD for a system drive for no more than a year (total run time) At any given time I have THREE system drives that I use in rotation so for my "system" I have to buy a new $40 HDD once a year
(I use 7200rpm 80gb drives for my system)
Though should also note that I am discontinuing use of 80gb drives for this purpose... I've already switched a 160gb drive into the rotation all future replacement HDDs ( the next planned for later this week) will be 160gb.
My "System" baclups will all be on 60gb partitions on 160gb drives christmas
This switch is based purely on delieverd price of a HDD.
It isn't purely the price of a drive but the price of a drive shipped, and frankly if Newegg offers free shipping on a $44 160gb drive it winds up being cheaper than an 80gb drive for $38 but costs $6.29 to have it shipped.
this is part of my switch from IDE drives to SATA system drives.
The size of the drive is irrelevant only the price matters
The thing is I prefered smaller drives because it removed the temptation
to use the drive as a data drive.... but I've lately taken to storing a copy pf my complete 160kBit/second mp3 library on a second partition on the extra space (in a seperate 100gb partition) on the system drive
NOTE: With a two drives OUT, one drive IN, cloned weekly, and rotated every four months that it takes three years for me accumulate a year's worth of "total run time" on any particular drive
AND after I've permanantly rotated a particular drive out of use as a system drive in my personal system it is STILL useful as a "pure data drive" for intermittant use OR to be used as a system drive in a "give-away" system....
How important do you consider your Data/Meta-data/system/system set-up to be?
How much time would it take you to reconstruct it all?
Because it isn't only your "pure data" you are protecting but your TIME in arrainging it the way you want it....
My heartfelt opinion is that you should be spending half as much time (cumulatively) protecting your data and setup as you would recreating it in the event of a worst case failure.
it may seem tedious, but it's better than the alternative.....
How many copies you have and more importantly how often you make cloned copies is dictated purely by your own paranoia.
My "Data" is backed up as often as I make any additions, often daily!
(and sometimes more often) I always have atleast four copies of