TM requires more space - must be an answer?

It works fine here.

How much space is used on your disk and how big are you timemachine backup disk? The timemachine backup disk should be 2-4 times bigger than your data. Are there something you should exclude, like virtual machines images..

I am not sure how up to date this information is, but you can see if anything is usefull here:
http://pondini.org/TM/C4.html
http://pondini.org/TM/Home.html

 

OP wrote above:
"i am forever encountering this constant frustration of TM requiring more space to complete the latest/current backup."

That's how TM works -- backup after backup, each consuming more space, forever and ever.

If you want to END that, once and for all, my suggestion:
Stop using TM and go to a "cloned bootable backup" paradigm of backing up instead.

You can created a bootable cloned backup using either CarbonCopyCloner or SuperDuper.

With CCC, you can even set it to maintain a clone of your recovery partition on the target drive.

And you can also tell CCC to archive "old, removed" files -- that is, older versions of files (from older backups) that you have deleted from your source (main) volume.

Do this, and you will find your backup drive doesn't get its free space "eaten up" by an ever-ravenous Time Machine...

 

I don't think that is exactly OP's problem. Rather that it cannot manage erase older backups and make room for the new backup. I don't have that problem.

On network drives TimeMachine uses sparse bundles. I have mounted them in diskutility and set the partition size to a fixe size. So on my 2TB timecapsule, iMac Timemachine only uses 1TB and no more, while my Macbook Air has a 0.5TB TimeMachine backup and the rest is used as NAS.

 

TM needs to move over files that change between backups. One problem could be if you are using virtual machines which use a large virtual disk for storage. Any time you run the virtual machine, the virtual disk changes and TM wants to copy the entire virtual disk again. This could rapidly add up to lots of space on backups. So, question to the O.P., are you running virtual machine for things like Windows, etc?

 

What software do you have installed on the computer?

 

Screenshot shows you are also using TM to backup "Storage", how much space is used on that?

 

I experienced the same issue on my iMac with a 2TB external drive for TM. Every time the drive would fill up, TM would show the same message as the OP, instead of properly doing its task of deleting the oldest backups and using that space to continue backing up new data.

I eventually surrendered to Apple's TM and purchased a 4TB backup drive. I now have 143MB left on this 4TB drive, so we'll see how TM behaves this time around. If it fails again, think I'll just use SuperDuper to do incremental backups. Strange how I find myself relying more and more on third-party solutions for OSX. Disappointing really.

 

TM has worked 'properly' in some senses, in that its deleted older backups to try to create enough space. However, thats not enough for what it thinks it need to do hence the message. The console log will show you it deleting the oldest backups before it gives up. To get the message it will have deleted everything it can, leaving just the latest. This is why you see only a single copy.

It could also be that what its trying to do is wrong, as Apple broke TM in Yosemite when it comes to external drives.

Symptoms to me look like:

• TM drive is relatively small, I'd guess <250GB (as from the sizes you quote +160 won't fit)
• TM has run with the external drive dismounted
• Now the external is reconnected and its run again

If this is the case then you have stumbled across the bit Apple broke. In the above circumstances, TM assumes in its space calculation that it needs to back up the whole of the external, not just the increment. Consequently the calculation is way out and it needlessly delete backups - see this thread here https://discussions.apple.com/thread/6625945