Time Machine - suddenly back up's fail...

[GilesM]

Hello,

I have been using an external hard drive as my time machine for years, then suddenly the back ups started to fail.
So I went in to Time Machine settings and found that the reported size of the next back up was greater than space that existed on the drive, then I noticed something odd, my Imac has an internal HD of 250GB of which 94GB is used.
However the next back up had a reported size of 490GB!

All my external drives (one for iTunes, one for video content) are excluded, and yet the estimated size of the back up is 490GB from a 250GB drive...

So, I erased the drive, so now it's empty and ready to take a back up, but with such a huge estimated size it will not fit...

Any ideas why suddenly Time Machine thinks there is 490GB to back up from a 250 GB system drive with only 94GB used?

 

[QuarterSwede]

Did you try turning off TM then back on the see if it would try to recalculate again?

I had a similar problem a while ago where TM filled up and refused to delete the old backups. Luckily, for me, a wipe of my external TM partition did it the trick.

 

[GilesM]

yep, tried that. I have performed a couple of re-boots of the imac (with and without the time machine drive attached) no luck....