Time Machine not doing hourly backups on El Capitan
I noticed on Oct 21 that my Time Capsule had not performed an automatic hourly backup of my Mac Pro since Oct 17. Time Machine Preferences said it would perform an hourly backup at a stated time less than an hour in the future. However, I tracked it over the next 24 hours and saw that it kept advancing the scheduled hourly backup by about an hour but did not actually perform any of the promised hourly backups. I went into Time Machine itself and confirmed that none of the hourly backups were present, and I also examined the backup disk in the Finder with the same result. I ran a full backup yesterday, and that worked correctly, but automatic hourly backups are still failing silently. Holding down the Option key while opening the Time Machine menu in the menu bar, I ran Verify Backups and got a report from Console.app that "Backup verification passed!" I filtered the Console log on "backupd" and found that, although backupd reports when I verify backups, there is no hint that backupd has tried to perform any automatic hourly backups.
I also examined my MacBook Pro, and it is experiencing the same failure. I ran a full backup of the MacBook Pro, and that worked correctly. The automatic hourly backups continue to be promised but never happen.
Googling the problem, I found similar reports here: <http://apple.stackexchange.com/questions/210832/why-doesnt-time-machine-do-sched uled-backups-after-my-yosemite-el-capita…>. These reports indicate that people have tried all sorts of remedies, including completely removing the Time Machine backups volume and starting over again, without success. The problem reportedly affects external backup disks as well as Time Capsules like mine. The problem started for me days before I installed OS X v10.11.1 on these two machines, so the problem apparently began in OS X v10.11.0 El Capitan.
My wife's MacBook Air is on the same network, but it is still running OS X v10.10 Yosemite -- and her automatic hourly backups are working correctly to the same Time Capsule. Her Console log shows several messages every time an hourly backup begins and proceeds. So the problem was clearly introduced in El Capitan and must be a bug in the new operating system.
This is on my home network. Both of my Macs are wired into the network using Ethernet cabling built into my home. My wife is running on wi-fi so she can easily move her Mac around the house. I am confident that this problem does not point to the Ethernet network as the culprit, however, because I am able to move all manner of files from Mac to Mac, examine the contents of the Time Capsule disk in the Finder, download files over the Internet and surf the Internet, all over the wired network through the Time Capsule without difficulty.
This is an urgent and critical problem, because most users rely on Time Machine for automatic hourly backups and, like me, can go for days without checking to make sure it is still working.
Mac Pro, OS X El Capitan (10.11.1)
