Why are TM backups made during power nap not shown as latest backup in TM preferences?
MacBook Air, iOS 10.0.2
In answer to my own question, I assume that TM backups during power naps are only made to the local hard disk and not to the Time Capsule (which in my case would require Wifi use). If that is the case, the latest backup indicated would be the latest to have been completed on TC although hourly backups were made locally in the mean time.
Have seen since that a TM backup made during power nap did show up as last backup in TM drop down menu. This leaves the question: why would it in one case but not always?
Having observed Time Machine stopping using my Time Capsule twice since upgading to Sierra, I have been investigating what has been going on by looking at the messages being logged during backups. In my case, it seems that every attempt to backup to the Time Capsule whilst Power Nap is active is failing. Essentially, at varying intervals into the backup, the TC volume is becoming unmounted, such that attempts to write to the volume are failing. Backups whilst the iMac is not sleeping work just fine.
I am in the middle of an experiment - having turned off Power Nap, there have been no failures for 48 hours (though clearly fewer backup attempts as they don't happen whilst the Mac is sleeping), and I have just turned Power Nap back on and am leaving the Mac sleeping to see if the backup failures re-occur. I fully expect them to.
Testing is a little time consuming as my backups rotate round 3 Time Machine volumes, only one of which is a TC. I'm running 10.12.1 on a 2014 27inch Retina iMac with a fusion drive, with a generation 5 Time Capsule connected to the iMac by Ethernet and WiFi, with the Ethernet being the preferred route (and the traffic flow suggests that it is). I would have had a better understanding of what was going on if the Console application hadn't been improved (ruined) in Sierra. At least I stumbled across some appends that suggested some Terminal commands that allow me to strip out the Time Machine messages.
I will add more comments as my investigations proceed.
time machine power nap
