Do you also check for data integrity?
I started doing that for my private backups as well when I got into the 'backup business' in a former job.
Just recently I wanted to copy data from an old Raid-5 array to my usb disk and the thing failed on me. It had not been used for 2 years (the raid box) and 2 disks failed... or at least the raid controller didn't like them anymore.
Now I did make a copy of that data 2 years ago onto another usb disk and immediately ran an MD5 check on it and the data was still fine. Now the big question is this:
"Was the data valid, when the MD5 sums were created?"
My current backup strategy:
- internet server runs daily backups using dirvish + md5sums
- an old backup is stored at my parent's - off-site backup
- a copy of that one is on a 2nd usb disk at my place
- at the office I use GIT for everything important
- my office data is synced with my internet server and my home pc
So at the end of a working day 3 disks in 3 different machines in 3 different locations would have to fail to give me a serious headache. GIT effectively saves me from propagating stupid mistakes into my backups.
You can't be paranoid enough with digital data. I'm thinking about putting one disk into a bank vault - on 2nd thought make that two disks of different brands and different usb adapters.
Maybe I've posted this one before, but 'The Tao of Backup' is always a good read.