Time Machine says needs more space


My Drobo (Gen 2) has been happily working on my Mac Pro (10.9.5) with Time Machine. The automatic back ups stopped working a few days ago saying:

“The backup disk needs 362.69 GB for the backup but only 217.16 GB are available. Select a larger backup disk or make the backup smaller by excluding files”

On the Drobo dashboard it says 2.71TB Used Space 915.98GB Free Space 3.60 TB Total.

I’d really appreciate any advice, thanks

hi gherkin,
can i check if your time machine is actually using a particular drive letter / or volume, and how many volumes you have?

it might just be that the drive letter/volume that you are using for time machine, is not having enough space for what it wants to do, and that you might be able to simply move some of your own other data files from that drive letter, onto the other volume, to essentially shuffle the free space around, and to try again?

(if you can, try to use the copy and paste method first, and then only deleting after the paste was successful)

if dashboard shows you to have about 900GB of free space, then freeing up about 150GB should be posisble, but please always do try to use dashboards overall free space for future backups etc, just so that the risk of overfilling your drobo is kept to a minimum, (or ideally prevented)