Time Machine Not Making Weekly Consolidations

[NaOH]

This is a 10.7.4 system and I've never used third-party utilities to tweak the default Time Machine settings. What I've noticed is that Time Machine is no longer consolidating daily backups into weekly backups. The last weekly backup was 14 May, and since then I only have daily backups.

I've run Disk Utility > Repair Disk multiple times, and no issues have been listed any time. I've turned off Time Machine then waited a few hours before re-enabling it. Similarly, I've turned it off, restarted the Mac, then waited a while before turning it back on. I found nothing applicable at James Pond's great site covering all things Time Machine (http://pondini.org/TM/Home.html), and my web searches also turned up nothing.

Anyone have suggestions for correcting this?

[trevor]

Is it because you have plenty of space on your Time Machine volume, and don't need to consolidate the daily backups into weekly backups?

Trevor

[NaOH]

I do have plenty of space on that volume (37.5 of 68 GB are available), and I always have had ample room. But my understanding was that Time Machine automatically does the weekly consolidations, not to mention that it did them for the the first 9 months since this Time Machine volume was created.

[benwiggy]

What method are you using to confirm that the consolidation isn't happening?
Checking the logs? Or looking at the files' datestamps?

Perhaps the log messages aren't being made, but the consolidation is occurring?

[NaOH]

I noticed just by looking at TimeTracker (http://www.charlessoft.com) (by the same developer who makes Pacifist), a free utility that "displays the contents of your Time Machine backups, and shows what's changed since the previous backup." I use TimeTracker periodically to check backup sizes. I do this because I exclude lots of files (with System Preferences) and its GUI gives me a simple way to see when there are large backups, often because of something new that I forgot to exclude. An example would be the fact that I use the WebKit nightly builds for my browser. I have no need to ever back that up. If I forgot to add that to the Time Machine exclusions, I'd likely catch it when there's a 150+ MB entry in TimeTracker. I can then simply remove it from previous backups (by entering Time Machine) and exclude it from future ones.

But to the bigger point here, if I enter the Time Machine interface, I also see daily backups listed along the right as far back as May 14, and before that it's all weekly backups. That doesn't seem like a log-file issue, but I'm not qualified to firmly make that determination.

[ganbustein]

The last weekly backup was 14 May, and since then I only have daily backups.

That is correct behavior. To quote what Time Machine says, right on its preference pane in System Preferences:


Time Machine keeps:
• Hourly backups for the past 24 hours
• Daily backups for the past month
• Weekly backups for all previous months

The oldest backups are deleted when your disk becomes full.


14 May is about a month ago. The next weekly backup will be for 21 May.

By the way, Time Machine does not ever "consolidate" backups. It prunes away snapshots as they expire. The snapshot that you have now for 21 May is exactly the snapshot that will eventually get promoted to a weekly backup. Between now and then, the intermediate snapshots will be pruned (i.e., discarded) one by one as they reach one month of age and expire. A file that you created after 14 May (so that it was not yet available to go into that snapshot) but deleted before 21 May (so that it was no longer available to go into that snapshot) will be discarded by TM one month after you deleted it, on the day TM prunes away the last daily snapshot that saw the file. It will not get "consolidated" into some other snapshot.

[NaOH]

14 May is about a month ago. The next weekly backup will be for 21 May.

I intentionally waited until a month had passed before posting this because, honestly, I couldn't remember when the weekly backups were created. I didn't think about it in terms of weeks. So I'll wait until the 22nd and confirm it's doing it then.

[NaOH]

And while I'd swear that there were daily backups until 14 May, double checking TimeTracker now only shows daily backups until 18 May (with nothing between it and 14 May). I'll wait until the 25th or 26th of June.

[benwiggy]

TimeTracker seems to fall into the category of those utilities that let you worry and check that your computer is doing the things that it is supposed to do in the normal course of its operation, like Little Snitch*, and various other process watchers, memory managers, etc.

For me: life's too short, and I've got quite enough to do with stuff that I want to get done, without worrying about whether the operating system is ... operating.

Obviously, checking that your backup is in order is a necessary and important task. But unless I get evidence to the contrary, I'm going to assume that the OS is working properly and get on with my work.

* See the posts here and elsewhere "OMG what's this ntpd that Little Snitch says is sending messages!"

[ganbustein]

I intentionally waited until a month had passed before posting this because, honestly, I couldn't remember when the weekly backups were created. I didn't think about it in terms of weeks. So I'll wait until the 22nd and confirm it's doing it then.
Don't think of it in terms of "creating" a weekly backup. All backups are created as hourly backups.

Hourly backups expire in 24 hours (or whenever, because of overzealous use of "Back Up Now", there exist 24 or more newer hourly backups). When an hourly backup expires, it either gets promoted to a daily backup (because it's the earliest remaining backup of its day) or gets pruned.

Daily backups expire in one month (which I think means 30 days). When a daily backup expires, it either gets promoted to a weekly backup (because there are no remaining backups less than 7 days prior) or gets pruned.

In your case, you have a backup that was created 14 May. It was created as an hourly backup, but on 15 May got promoted to a daily backup. On 13 June (30 days later) or on 14 June (one month later) it got promoted to a weekly backup.

Until 21 May, the existence of that 14 May backup prevents daily backups from getting promoted to weekly backups. They will instead expire and be deleted. When the 21 May backup becomes a month old, it will get promoted to a weekly backup.

If you were to delete the 14 May backup before then, the oldest daily backup would get promoted to a weekly backup to replace it. That daily (now weekly) backup redefines the "beginning of week". Thus, if it's the 19 May backup that gets promoted, the next backup to get promoted to a weekly backup would (barring further meddling on your part) be the one that is currently your daily backup for 26 May.

There is nothing hardcoded into a backup to identify it as hourly/daily/weekly. As I say, each backup is born as an hourly backup, and is thereafter immutable. Instead, TM re-evaluates the status of all remaining backups immediately after completing an hourly backup. (This all happens during the "cleaning up" phase of a backup.) The oldest backup is unconditionally marked as a weekly backup. Each backup that is more than a month old is then marked as either expired or weekly, depending on whether it follows the previous weekly backup by less than 7 days (time of day is ignored) or at least 7 days. Each backup that is less than a month old is marked as a daily backup if it's the first backup of its day. Up to 24 of the newest unmarked backups are marked as daily (but only if they're less than 24 hours old). All unmarked backups are marked expired. (All of this "marking" happens in RAM only. Nothing is written to disk or otherwise cast in stone. Nothing changes inside a backup when it gets promoted; it still has exactly the same files it had before, no more and no less. There is no "consolidation".) Up to five of the oldest expired backups are then deleted.

[NaOH]

Great explanation, ganbustein. And that's clearly what's going on as daily backups now go back to 19 May, not the 14th or 18th as I noted earlier. I didn't remember what I'd seen in the past, but I clearly screwed up in thinking through what I should be seeing. Thanks for clarifying and setting me straight.

And now that I know Time Machine is properly doing its thing, I'll begin using a Time Machine backup strategy (http://hintsforums.macworld.com/showthread.php?t=128739) I learned from you in another thread (see comment #10), to make weekly backups of my Time Machine volume. So, double thanks.