Does Time Machine Work?

None of my Macs use only one Time Machine destination. Most of them back up to at least three separate devices, so my TM preferences don't show the time of the next scheduled backup. To show that I'd have to temporarily remove all backup destinations but one.

Here is a Time Machine log excerpt filtered for the word "Created" over the previous 24 hours. That's probably much more valuable because it shows a record of actual, completed backups.

(For some reason I couldn't post the log, so here's a screenshot of it including whatever "invalid characters" it contained)

One backup appears to to missing, at about 0420 this morning. I can only guess that it had nothing to back up at that time.

The backup at 1552 yesterday may have been a manual backup that I did out of curiosity, at or about the time I posted my previous reply. I don't care enough to recall or be certain of that. If my most recent backup is recent, that's all I need to know.

If your Mac isn't doing what mine is, it's not surprising. Everyone's activities are different. You probably don't use your Macs the same way I use mine.

John Galt wrote:

It's the output of a crude bash script that I wrote to extract Time Machine log entries.

The macOS version is the current one.

Do you mind posting that bash script?

From terminal I can see hourly local snapshots, but not so nicely, it helps to drag the window wider:

(maybe you had something to do with this script?)

log show --predicate 'subsystem == "com.apple.TimeMachine"' --info

John Galt wrote:

That's all there is to it, but using the --last option limits its output to the specified time period. Otherwise log extracts its entire history and will take forever. The rest is just filtering for the desired string and formatting. "Created" is just as good as any number of other indications that TM actually finished.

The log entries will be different for desktops vs. portables and I did not bother to include a check for which one (which is a good question since the OP didn't indicate which he has, and TM on portables includes local snapshots).

Thanks John Galt— this gets me much closer !

verifying the hourly Time Machine Local Snapshots from the log files:

No, not mine. Mine backs up every hour, except when my Mac is asleep.

I don't know why it isn't working for you. Use Console to search the system.log for the string backupd. Post the results here, it may give a clue for what's going in.

danallenhouston wrote:

Is any data available showing the percentage of mac computers keeping consistent hourly backups for more than a few weeks? My model indicates the number is less than 10%, but my model is likely to be off by +20%/-5%.

I can tell you, for a robust back up strategy you need more than just Time Machine. It does work well for what it does seamlessly in the background. I would not recommend trying to micro manage or interpolate the nuance of hourly backups.

I would recommend letting it work for a while and see how it levels out over time. It is fairly painless just to let it do it's thing.

You can read more on backups here, Time Machine and Local Snapshots included: How to create a boot clone

That particular script cited in that article is even more crude. I don't use it any more and I don't recommend anyone else does either. The cut command is a poor choice for formatting, besides, there have already been changes to log as well as Time Machine that have already rendered it outdated. The reason I created it was that Sierra introduced a new unified logging system that precludes simply using grep with system.log as was possible with previous OS X versions. We can anticipate that similar uses for system.log will soon be outdated also, if they aren't already.

An updated general purpose script follows, but beware it is for desktops only (since local snapshots apply to portables) and it is likely to become outdated upon the very next Sierra update:

clear; printf '\e[3J' && log show --predicate 'subsystem == "com.apple.TimeMachine"' --info --last 48h | grep -F 'eMac' | grep -Fv 'etat' | awk -F']' '{print substr($0,1,19), $NF}'

It extracts certain relevant Time Machine - related activity for the previous 48 hours. To change that period change that value. It's not the only way to extract TM logs but it works for my needs. It might not apply to the needs of others.

It makes hourly backups for a day, daily backups for a week and weekly backups for as long as the drive you are using to save them has space on it. Keep in mind that it does not do a complete backup everytime. It simply backs up changes from the prior backup.

But Time machine will only make a backup of your 'data', not any system related files (i.e. it only considers files within your User folder). So if you do not make any changes (e.g. over night), no backups will be created.

If you have a file open and are editing it, unless you make constant saves, it will not be flagged for backup until you Save/Close it.

You will also see that there is only one backup per day for days beyond 24 hours ago. So you have one per day from 2017-01-26 backwards, where the hourly backups for those days have been aggregated.

AndrewCSP wrote:

But Time machine will only make a backup of your 'data', not any system related files (i.e. it only considers files within your User folder).

That is completely false. Time Machine, by default, backs up everything. You can make it not back up system files, but by default it does.

Time Machine only backs up what has changed. If there were no changes to the file system, nothing will be backed up in the hourly backup. Unless Apple has changed this, it will not back up open files. If you start editing a document and leave it open all day, it will not be backed up until you close it. In the past it would not back up an open iPhoto Library. I do not know if that still applies with Photos.

This site is a bit old, now, as the author passed away a few years ago, but it has quite a lot of still relevant information on Time Machine: http://pondini.org/OSX/Home.html