My levels of paranoia...well might exceed many of you - but I blame my career.
As a PhD student one of the first things I was told was the horror stories of the old floppy disk backup and losing your PhD entirely (and it happened to people). My approach for that is:
Macbook 320 gb Harddrive which has all my PhD stuff
Backup 1 - 750 gb portable (find they are more reliable and tougher) with all my data (the stuff that took the past year to produce) plus full Mac Backup at home
Backup 2 - 500 gb portable with duplicate of the above minus a few less critical original datasets stored at office.
Backup 3 - 500 gb portable as above, updated monthly stored at parents farm in NE Vic
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My backup procedure is weekly, additionally all backup materials for source data, code, important musings are stored on the university server. I always have either the home drive or the Mac with me any time I am away from home.
So you can imagine it gets complex...but wait - theres more.
500GB PC laptop harddrive - past 3 months photography or working files.
1TB desktop drive (my only of this type, otherwise portables) - General storage - contains website copy, music files, plus all my other digital media.
500 GB drive - Photo Drive 1 - All photos archived.
Photo Drive 2 - As above, full backup of all photos, stored in office.
Video Drive 1 - Storage for storm Video, 500GB drive.
Video Drive 2 - Backup for the above and overflow, stored in office.
DVDs - The top tier shot archives (A grades) and any job archives are put onto DVD as additional backup and for quick reference.
Grand Total - ~5.5 TB storage give or take. Given my uni work original data space numbers 5-10 TB...not too bad
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And yes - I realise it probably sounds paranoid - but think about spending 3 and a half years on something only to lose it in the final stretch. The same could be said for my storm images - I would be heart-broken. One EMP and we are all stuffed though :P.