I cleaned backup disk as it was full and started a clean (empty) Time Machine backup. On a disk of 465Gb my data occupies 321Gb. Time Machine has started backuping files and I found interesting that estimated backup size was increasing during the day. Left it to work overnight, and in the morning at time of writing it has backuped 485Gb out of estimated 533Gb. The difference between backuped files and estimated full size is increasing as I see.
How is this possible? What went wrong? Should I exclude some folder?
The Mac is OS X Yosemite. Time Machine worked correctly before upgrade.