Bootable Time Machine Restore Disks
My data protection philosophy is one does not need a backup system; one needs a foolproof and tested restore system. So I talk about restore volumes, not backup volumes.
I followed PlotinusVeritas' advice and purchased Carbon Copy Cloner to create a clone of my internal storage as my fourth restore disk. Great advice. I will keep this cloned volume offsite as a medium-term archive. Having used CCC for cloning I now use it for a different purpose. I do not need a bootable clone onsite for my emergency restores.
New procedure: Each Time Machine disk can be bootable if one runs CCC on them to prepare them with a bootable recovery partition upon initialization. This simple innovation avoids the need of keeping around a cloned disk with its recovery partition. My onsite, bootable restore disks will be up-to-date as of the last TM snapshot.
If I used a cloned disk as an emergency quickly-bootable volume, the changes between the clone time and the last TM snapshot would be lost. For me, this loss of data is not worth saving the few hours of TM restore time to get back on my feet after an system volume failure.
How might one easily create a bootable recovery partition without using CCC or other for-fee utilities?
P.S. Creating bootable recovery partitions on freshly reformatted TM restore disks should be a standard TM feature (a la CCC). I will submit feedback to ask for this change.
P.P.S I tested restoring from my bootable TM restore disk. I booted from the TM disk's recovery partition. I selected that disk's TM volume as the source and a freshly formatted external disk as the destination. It erased the target disk and then to my horror said it was erasing my SSD system volume. I powered the Mac off immediately. It apparently did not get very far because my SSD system volume and its recovery partition are intact and Disk Utility verified my system filesystem is OK. Whew! This is a major bug in TM. I will report it as well.
MacBook Air, OS X Mountain Lion (10.8.5)