About Time Machine and backup

[Pinkly Smooth]

Hi everyone.
I have an iMac and I was suggested my someone to have a strong back up strategy that he said should comprise of a:
Time Machine on its own External Hard Drive (EHD) which ideally should have a storage capacity of 1.5 to 2 times that of your Mac's Fusion Drive (i.e. 3 to 4TB) - because my iMac has 2TB.
And a bootable Cloned BU, such as Carbon Copy Cloner or SuperDuper! Again, on its own EHD (3 to 4GB)
Can someone explain the difference between the two? What is the purpose of the bootable cloned BU?
I have gathered I need to buy an external hard drive, to store and save what is inside the iMac, incase it crashes and I lose what is within the iMac.
And with regard to the bootable cloned BU, out of the two options I was given (Carbon Copy Clonder or SuperDuper) which one is better?
Does all of this mean, that I will have to buy two External Hard Drive, one for each?
Thank you.

 

[Longkeg]

Time Machine is very easy to set up and runs behind the scenes. It saves the state of your hard drive automatically so your backup is always up to date. It's good for rescuing files that were accidentally deleted. You can also go back in time and see old documents and their various saved states from days, week, months or even years ago. As long as your iMac is functioning correctly it's all you'll ever need.

It's when your iMac isn't behaving itself that Time Machine shortcomings become apparent. Should your internal boot drive fail your only option is to install another drive or connect to an empty external drive and have TM restore everything for you. It's a process that can take hours and during that time you won't have a working iMac. When drives fail some of those critical system files get corrupted and TM will happily keep backing up those corrupt files that are critical to a restored system. Your new system may have the glitches that were saved and exported by TM.

Now a bootable clone is a snapshot in time that represents all that was good and perfect about your iMac. Unlike TM, a clone will not automatically update itself (there may be software that that can do this though). To stay current the whole cloning process must be repeated periodically as the saved state of your HD changes. The advantage is that you can start and run your computer from it. Like having a spare brain should something go wrong with the one you were born with. Should the main hard drive fail you can just plug in the external clone and get right back to work. Assuming the clone is up to date you may not even be aware that anything is different about your iMac.

These two backup strategies should cover 99.9% of all the bad things that can happen to a hard drive.

 

[Pinkly Smooth]

Hi Longkeg, thanks for the reply. I would like to ask, are two EHD's required? One for each?
You said that the Time machine on its own EHD is all I've ever need but then you say at the end, that the two backups should cover everything and all the bad things that can happen to a hard drive. Do I really need both?
And regarding the bootable clone, which one is better, is it Carbon Copy Cloner or SuperDuper.
When you talk about an empty external drive should my internal boot drive fail, are you referring to the EHD, external hard drive that connects with Time Machine? Sorry I am very new to all this.
With regard to the difference between the bootable clone and Time machine, is, if I understood this right, is if everything fails, I can still use the iMac from the bootable clone connected to the iMac without having to wait at all? Where as with the Time Machine, I would have to wait for that to happen? Other than that, they seem to do the same thing. Is it important to also have the bootable clone in case something goes wrong, and the bootable clone is much better for that situation. Also the bootable clone doesn't carry any of the problems or glitches time machine does. Is that accurate? If the bootable clone is so much better, why even need a time machine? Do both programs work together.
I am still unsure of the difference between both. Thank you.

 

[Fishrrman]

A bootable cloned backup is (at least as far as I'm concerned) far more usable in a "moment of need" than is a time machine backup.

It is AN EXACT COPY of your internal drive.
You can boot from it, and you won't be able to tell the difference (unless you check "about this Mac" to see which drive the computer is booted from).

I've seen too many posts (many MANY posts) in this forum from people who are trying to access their tm backups in a moment of need and... CAN'T get to them.

Not so with a cloned backup.

Both CarbonCopyCloner and SuperDuper are free to download and try for 30 days.
Easy enough to try -- and see -- for yourself.

 

[Pinkly Smooth]

A bootable cloned backup is (at least as far as I'm concerned) far more usable in a "moment of need" than is a time machine backup.

It is AN EXACT COPY of your internal drive.
You can boot from it, and you won't be able to tell the difference (unless you check "about this Mac" to see which drive the computer is booted from).

I've seen too many posts (many MANY posts) in this forum from people who are trying to access their tm backups in a moment of need and... CAN'T get to them.

Not so with a cloned backup.

Both CarbonCopyCloner and SuperDuper are free to download and try for 30 days.
Easy enough to try -- and see -- for yourself.

Ok thanks! So its better, for the reason you listed, to have also a cloned backup. Do both time machine and the bootable clone, require their own EHD? Since cloned backup is so much better and more efficient, why even bother with the time machine? Do you have to have both, to have maximum protection with regard to the hard drive.

 

[ApfelKuchen]

There's one very important reason for using separate external HDs... If you use the same drive for both backups, what if that EHD fails?

Further, Time Machine does prefer to have a drive of its very own (it's likely to function more reliably). Drives are cheap and getting your data back can be very expensive, so my philosophy is, go with Apple's recommendation to dedicate a drive solely to Time Machine.

If you have external drives that also need to be backed up, Time Machine can do that. In System Preferences > Time Machine > Options... you can choose to include/exclude other drives connected to the Mac.

Some would normally mention that a really good backup scheme would include off-premises backups, such as in a bank safe deposit box. Cloned backups are particularly good for this purpose, as you don't expect them to be part of an up-to-the-minute backup plan. A classic approach is to have two or more drives for cloned backups. Make the backup, take it to the bank, "withdraw" the backup that's in the bank and use it for the next cloned backup. Lather, rinse, repeat.

Finally, why use Time Machine at all? Because it's an automated, full-time, incremental backup method. It backs up everything that has changed over the past hour, every hour. It then allows you to go "back in time" to recover either individual files, or previous states of the Mac (such as prior to installing the latest macOS version). "Snapshot" backups like a clone are only as good as when you last made one (remembering to make a clone of the Mac before every OS upgrade, for example).

Now, Time Machine isn't the only way to make an automatic, incremental backup. However, since it is built into the OS AND Apple builds "Restore from a Time Machine backup" into the OS's Recovery system, it's definitely the most convenient to work with.

 

[Longkeg]

Potable Clone: Good
TM Backup: Better than nothing
Both: Best

Clone Pros: exact copy, bootable

Clone Cons: it’s only as current as the latest backup (if you’re working on a file you created in the morning and your HD fails, the clone you created last week will not have that file on it)

TM Pros: totally automatic, all files are backed up within an hour of being created.

TM Cons: not the best for times of critical need, can export glitchy files and cause problems during HD restoration.

Separate HDs: Ideal
Single HD: problematic

If you only have one drive I would partition it with two volumes to separate the two entities.

 

[Pinkly Smooth]

Thank you guys for your help. You are so helpful and kind! Thanks again.