Time machine not backing up Mac Mini El Capitan 10.11.6

[JUGK]

On both my Mac Mini [late 2014] and Macbook Pro [late 2012] Time machine is not backing up. I get failure notices and there is no way I can see to make a "back up now' I need to back up my personal files, emails etc as I am trying to upgrade the Apple software. My WD 3TR back up disk has plenty of room over 2 TB. How can I get Time Machine to work? It has been failing for months and I only now started getting the fail messages. Time Machine opens and I get a blank page of desktop and a lot of red failed lines in the right. Please help.
Thanking you. Jugk

 

[satcomer]

So when the drive is connected you don't het the Time Machine file backup If you wanted the boot from that drive then you want a bootable clone!

 

[JUGK]

The time machine now is sending me a message each time it tries to back up that the back up failed. Both Mack Mini and Mc book Pro are having the same "failed backup' notice and both have their own WD 3TB back up disk attached at all times. I have no idea how a clone is made or what to put it on. Please help by explaining and direction as to what I need. Thank you

 

[HDFan]

The time machine now is sending me a message each time it tries to back up that the back up failed. Both Mack Mini and Mc book Pro are having the same "failed backup' notice and both have their own WD 3TB back up disk attached at all times.

I'd run a repair utility on those disk, such as first aid in Disk Manager.

How old are the disks?

TM disks just tend to fail. I would make sure to have some bootable clone backups (such as those made by Carbon Copy Cloner) just to be safe.

 

[Boyd01]

I would get another disk and see how that works. I agree that you should make a clone ASAP to protect your data. That can be done with Carbon Copy Cloner, you can just use the free trial although it is well worth the purchase price. Again, I think you need a new disk for that to insure its integrity. Going forward, it's a good idea to have both clones and time machine backups on separate disks.

When you get this sorted out, you might give some serious thought as to whether you should upgrade to a newer version of MacOS. El Capitan is no longer supported and (more important) stopped receiving security updates a number of years ago. Mojave is oldest version that's current supported but that is expected to end soon.

 

[Fishrrman]

As Boyd suggests above -- try CarbonCopyCloner.
It's a backup utility that won't let you down in a "moment of extreme need"...