sdbackupbytime?

[Dan Lester]

I believe, over the years, there has been some discussion about this, but ...

Most of my backups are automatic. In the wee hours of the morning, when I can't monitor them. But every month or so, I do a special manual backup. Today, I did one. The backup was successful, and completed, according to SuperDuper but, after that, the disk and OS was VERY busy for many minutes on what Console told me was sdbackupbytime activity.

Um. Whazzat?

Eventually, everyone is happy, and the disk activity ceases. But when a backup is formally completed, according to SuperDuper, do I have to wait for everyone to be happy? Or can I just unmount the disk while it sounds like it is working hard? After SuperDuper SAYS it is done, it's apparently not.

[dnanian]

sdbackupbytime does not do disk activity, so I don't think that was it. The activity was either Spotlight or an antivirus program.

If you have sample logging from that, though, send it in to the support email.

[Dan Lester]

Ah, OK. Thank you. So the frantic disk activity wasn't connected to the frantic OS activity with sdbackupbytime that was being reported on Console. But that's ALL that Console was reporting. If it was Spotlight activity, wouldn't that show up on Console as well?

I don't use Spotllght, and I have unchecked all the "categories" in Spotlight prefs. So I was presuming that Spotlight wasn't indexing anything. I guess to disable Spotlight indexing entirely I have to get rid of /System/Library/LaunchDaemons/com.apple.metadata.mds.plist. I will do that.

But out of curiosity, what exactly is sdbackupbyime doing at the end of a backup?

[dnanian]

sdbackupbytime is doing nothing after a backup that's different than what it does normally. If you're seeing differently, I'd need to see the logging.

Basically, it's the daemon that's managing time-based backups, sleep management, etc.

[Dan Lester]

Whoa. OK. So the frantic activity of sdbackupbytime didn't even have anything to do with the disk backup I just did? By that token, I guess the answer to my question is that sure, when the backup is complete, feel free to dismount the backup disk, even though sdbackupbytime is busy. I had mistakenly assumed that having just done a backup with SuperDuper, activity on the backup disk was due to SuperDuper, and sdbackupbytime activity pertained to that backup disk. Confusing!

Previous forum posts were complaining about sdbackupbytime hogging the system. That wasn't what I was concerned with, and I presume that those original problems with sdbackupbytime were fixed.

[dnanian]

Again, I don't know what "frantic activity" in this case means, Dan. I'd really need to see the logging...but I can say for sure it had nothing to do with the drive being 'busy'.

[Dan Lester]

Well. by frantic activity, I just meant that in the space of a couple of minutes there were about fifteen or twenty messages on Console that came from sdbackupbytime. No messages from any other app. Not to say that sdbackupbytime was overloading the OS, but just that it was the only thing happening.

But thank you. I think my original question was answered.

[Dan Lester]

Let me reinvigorate this discussion, Dave. I happened to look at my Console today, which I don't routinely do, and just about EVERYTHING there is sdbackupbytime! I mean, THOUSANDS AND THOUSANDS of sdbackupbytime INFO entries just in the course of a few hours. Whaaa?

Yes, let's call it "frantic". My Console entries are almost totally consumed by sdbackupbytime. sdbackupbytime is doing something every minute. Mostly at hh.mm.05.

See a few random hours of logs attached. The last few, in the afternoon.

What in the world is going on here?

BTW, SuperDuper isn't launched, and only does scheduled backups in the middle of the night.

[dnanian]

That's totally normal. It's a few lines, once a minute. Not frantic. That's how ASL logging works.

[Dan Lester]

OK, thanks. No question it isn't loading down my OS, but what in the world does it need to do every single minute??? My timed backups are once a day. Can't understand what it needs to be doing every minute. I will concede to call it "manic" instead of "frantic".

[dnanian]

It is neither manic nor frantic - once a minute only 1440 times a day. It's just not much logging, Dan. You should see what the OS is doing!

We run once a minute, and do informational logging once a minute to debug potential issues on user systems with scheduling, sleep, wake, etc. It's how scheduling works...

[Dan Lester]

OK, but I just don't see what it needs to be busy with. I mean, if I have a scheduled backup at 2am, what really needs to happen at 5:00pm, 5:01pm, 5:02pm or 5:03pm? I'm not familiar with how scheduling works, but it kinda sounds like thumb twiddling. Manic: showing wild, apparently deranged, excitement and energy. Can you elaborate, Dave?

[sdsl]

After staring at my own Console, especially under Devices which deposits scores of lines of text every second, this strikes me as much ado about nothing. I don't think you can call sdbackupbytime "deranged" unless you can send a snapshot of your Activity Monitor and show that this process is using significant cpu cycles and memory. If you want to see a lot of activity, look at your Console under Devices and it will make sdbackupbytime look like a piker.

[dnanian]

Periodic tasks run by launchd need a spec, in their plist, for when they should run. One daemon can either run "forever" and then schedule internally - which would take more resources, and kind of go against the whole way launchd is supposed to work - or it can use the existing system.

We use the existing system and run once a minute.
A wake event is, indeed, scheduled for the time of the next backup - let's say 5pm. And if the Mac is asleep, we're neither running not logging. The wake happens, and we run immediately and check what we need to do.

Smart Wake needs to run before the wake event (see the blog post about Smart Wake from a few years ago - I think It's called "The Best UI is No UI" - for a discussion of this). That's all handled by this little daemon.

When it runs, it performs a few tasks, and log informationally about those tasks in a relatively minimal manner - again, four lines of logging, once a minute.

The system is logging zillions of lines of logging all the time. We're logging four lines. Those lines are being logged to a facility that's designed to manage millions of lines.

It needs to do these things for SuperDuper to work. I don't do things randomly. They have minimal if any effect on your system.

Could I eliminate that logging? Yes, I could. But then when things go wrong, I wouldn't have any diagnostics to work with. That's why I'm logging in the first place.

You said there are "thousands and thousands of entries, just in a few hours". In a few hours - let's say three - there would be a total of 720 log entries from sdbackupbytime. Not even a single thousand.

Yes, those entries are a bit repetitive. That's because it's always doing the same thing. And it's logging information about that.

A daemon has no interface. It's a background process. I can't show status. This is how that status is logged.

What do I gain from this logging? Well, let's say someone indicates a schedule didn't run. The logging shows me what the daemon was doing around the time of the schedule. By examining this logging after the fact, I can determine whether the daemon encountered an error, or perhaps wasn't run by launchd for some reason.

This is the way things are done, using the facilities provided by macOS, in the way they're designed to be used.

[Dan Lester]

Thank you Dave. Those actions are certainly not loading down the system. I just find it curious that so much is going on. But I appreciate your explanation, and I will continue to enjoy using SuperDuper.