Thanks Honestone, I have not used Tech Tool or Discwarrior for 8 years or so. It just seems that Mac OS has gotten much better and they are irrelevant. I have not missed them at all. Should I get one/ other or both still? I think Discwarrior was the stronger solution for Mac Hard drive issues. Discwarrior I remember not having a recovery disk, whereas I remember an "e" disc from tech tool. You need both?
Once in a while, Disk Warrior can do some additional "magic" that no other disk maintenance/repair program can do. But, I have yet to run into such instances.
The most recent version of Disk Warrior also comes on a bootable flash drive (I have the prior version, so I would need to boot that after booting from my SD clone (if I want to do repairs on my internal SSD)). TechTool Pro has an eDrive feature, which is a bootable volume that allows one to do maintenance/repairs on one's internal drive/SSD. (It is actually similar to the Recovery HD partition in functionality).
The important thing to remember is that maintaining Macs (and external devices) is just like owning and maintaining a car. The more cleanup/maintenance one does, the occurrence of problems/issues becomes less and less. Myself, I use Onyx, TechTool Pro, and SuperDuper! once a week (typically on Saturday mornings) to cleanup, check, repair, and backup/clone my internal SSD on each of my Macs to an external device (I actually have two external devices that I can boot the SD clone from. I also am constantly removing unnecessary stuff from each of my Macs on a daily basis).
So, to answer your question, no, you do not need both of them. But for me, with the eDrive feature, TechTool Pro is easier to use.
That said. IF I use SD, and don't have either of those, then I'm screwed? or There is that option of booting online, but you can't do that right at crisis time?
If you have not been maintaining the external drive that the SD clone is on, then that drive could go bad. Using Disk Utility, TechTool Pro, or Disk Warrior to keep that external drive in as best of shape as possible would minimize the crisis you describe. Given that it is a mechanical device, there is only so much one can do. But, at times, you'll get some warning "signs" that the drive is getting bad, and thus can take action.
But yes, if the external HD (or external SSD) that the SD clone is on goes "kaput", you would be "somewhat" screwed.
Also, even it TM is not bootable, it can become the replacement Mac OS of choice still right? So even the SD clone does not need to be the first in the line of restoration?
A TM backup does not contain a backup of the OS. So, in a catastrophe (assuming the internal drive/SSD is still OK), the recovery process would be:
1. Some way, boot your machine "externally". If the Recovery HD partition is still OK, you can boot your problematic machine from it.
2. Erase, and Format your internal drive using Disk Utility (that feature is part of the Recovery HD partition. (Disk Utility will also tell you how "healthy" the internal drive/SD is (as will TechTool Pro)). I don't know about other methods (except by doing it from an SD clone).
3. Perform a fresh, "virgin" installation of the OS.
4. Re-boot your Mac, and then use Migration Assistant to migrate/copy stuff from the TM backup.
Final question: I currently don't bother to save the last OS. Should I? You just go to the apple store and find El Capitan and download it and keep it on the Mac HD? Or couldn't I just do that in a crisis anyway?
You can do it in a crisis, but why wait until then? You should be able to go to the App Store and download/re-download the latest version of the OS you are using. For me, that would be OS 10.11.4, El Capitan. (And yes, you should be able to download it). When the download is complete, a file entitled "Install OS X El Capitan" will be in the Applications folder. It is then best to make at least one copy of that file somewhere else (and in fact, copy it also to the device that your backup is on).
Again, as I described above, having the file somewhere else (and especially on a backup (SD in my case)) comes in very handy when doing a recovery/restore.
To sum all this up, quite a lot of this depends on the following:
1. Which backup tool you use.
2. How meticulous one is in performing disk cleanup, maintenance, repairs, and backups.
3. How old are the devices one has (by that I mean internal drive/SD, and external drive/SD).
