OSX based back-up strategies

Question

Having suffered a catasprohic disc failure and spending a few weeks recovering from it, I have leanred more than ever wanted to about diskutil. raid 1, time machines and hard disk encryption.
The disk unit that failed was a WD MYBook 3TB. While the disk itself was fine, the added PC board overheated and failed (apparently a common problem) on this unit. Unknown to me, was that the data was encryted at the hardware level.
Although the data was intact, the only way to get past the hardware/firmware encypton was to track down a similar sacrificial drive and replace the board. A generic case recognized the disk but not the data. It is important to note that buying a sacrifical news WD Mybook, will probably only work if the same model (and possibly reverision number) of the failed PC Board is used. That problem was solved with a ebay purchase - good luck, not great planning.
Lessons learned
- Hard disk firmware encyption brings new challnges. There is a reasonable chance your exterbal USB drive is encryted)
- Include an evaluation of the manufacture's recovery tools in your puchasing decision
- Diskutil can take days to expand an existong partition with data. If you need to expand a parition, back-up the data and start fresh
- Raid 1 (mirroring) writes take approxiamaley 3 times as long as writing to a single disk. It works but for me it is mot worth the transaction cost)
- Duplicate Time Machine back-ups cannot be done with a simple file copy.  Te trick is to shut off timemachine 
The new startegy
Back-up
Frequently accessed and modified data. (500 gb Internal Drive)
- Time machine back-up to partitions on two physical drives. TimeMachine alternates back-ups.
Infrequently Modified Data (2 3TB External Drives). (music, photos, and archived files)
- Create an initial copy on a second drive and rsync daily. Still experimenting with best option and automation (Likley will use crontab to run a script)
Disaster Plan (1 3TB Drive Stored offsite)
- Rotate redundant Drive2 with a Drive3) on a monthly or when otherwise warranted (Stil sorting out how best to do this with time machine)
- verfiy and repair disks on a monthly basis.
- Store documents and essential files on Dropbox and GoogleDrive daily. Working on a background script to automate the copy process of all saved files)
I have tested the subsitition of the external drive 3 for drive 2 and the removed Drive 1. On the to-do list is to create a bootable recovery disk to make recovery from an internal drive failure easier. The as yet, unaddressed huge hole is data security.
Any suggestions on how to improve my backup and disater recovery plan would be appreciated,  Of particuliar intertest is proven methods to protect sensitve data.
Thanks,

Answer 1

You need at least two complete, independent backups of all data, at least one of which is off site at all times. Don't rely exclusively on any one backup method, such as Time Machine. Encrypt your backups for security, but make sure it's impossible to forget the password(s). Think about what it would take to recover your data if your home or office, or both, burned to the ground.