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Time machine: how it really works?

M

macmba

macrumors member
Original poster
Aug 10, 2011
39
0
Well, after purchasing my mBA and putting everything I would on it, including VMware, Office, other apps, etc etc etc, well I made a backup about 2 weeks ago. The time machine created a folder with the date on it and everything is golden.

So I plug in the external HDD to make another back last night. From what I could tell, its as if it was backing up the whole HDD again, from the amount of GBs left. I thought its supposed to only do incremental backups, not a "from scratch" backup. Anyhow, I let it continue, and at the end I end up with another folder with yesterday's date and "revision number".

So now things look like this for example:

2011-28-07-12566
2011-13-08-14500

Now, does that mean I can delete the first folder and just keep the last one?

Then, when I added some small files, it seems that when the next backup was ran, it backed up a lot more than the size of those files. It seems it was backing up Gigs of data, and am not really sure why. At some point between yesterday and today, I ended up with 4 different folders like this for example:

2011-13-08-14500
2011-13-08-15600
2011-13-08-16900
etc etc

Can someone please explain how this thing is really supposed to work? Thanks.
 
Time Machine makes incremental backups, but if some rather large file keeps changing, it'll keep backing up that rather large file over and over again. Your best bet is to add that file to the exclusion list. You're sure it was completely finished the first time, right? It does take awhile.

As for the folder thing (warning this is a bit technical), Time Machine uses a UNIX technology called hard-linking. Essentially, every one of those dated folders appears to contain an entire backup of your disk, when in reality most of the data (files and folders) are hard-linked versions of the old previously backed-up data. Any folders that have changed have all unchanged files within them hard-linked, then it backs up the changed files. However, Mac OS X does not work with hard-linked folders well. Do not edit anything on the drive itself. If you want to delete a backup, go into time machine, navigate to the date you want to delete, then click on the "gear" icon in the fake finder window within Time Machine, and delete it.
 
Last edited:
Thanks. I figured its not as straightforward as deleting those folders. Actually the ALL of the folders add up to about 60GB, and my HDD is about 50 or GB, si its impossible that each folder is the whole backup. At this point, how can I pick the latest backup and delete everything else? Seems like its not duable. Unless I remove everything and just do a fresh backup every time I want/need to. Not very practical.

Example: if I did a backup 2 weeks ago, and 2 last night. Say I wanna keep ONLY the last one made, how would you go about doing that?
 
You're not supposed to make any changes to the time machine backups. TM keeps following backups:

Hourly for today
Daily for the last week
Weekly for the last month

The TM backup database will bulge to the maximum space you allotted to it. Once it reaches that size, it will start deleting the oldest of the backups.

The backups are incremental, not absolute, therefore two hourly backups complement each other, but are not independent. Do not delete anything inside it.
 
The backup sum will always be bigger than your current used space because it keeps versions for a period of time. If you edited a 20MB file, that now takes up 40MB in time machine, and that's fine. The system is supposed be set it and forget it, so quit worrying :D
 
macmba said:
Thanks. I figured its not as straightforward as deleting those folders. Actually the ALL of the folders add up to about 60GB, and my HDD is about 50 or GB, si its impossible that each folder is the whole backup. At this point, how can I pick the latest backup and delete everything else? Seems like its not duable. Unless I remove everything and just do a fresh backup every time I want/need to. Not very practical.

Example: if I did a backup 2 weeks ago, and 2 last night. Say I wanna keep ONLY the last one made, how would you go about doing that?
Click to expand...

Sorry, you must have missed the last sentence in my long post of geek crap. :D Go into Time Machine (the app, not the drive) browse to a date you want to delete, click on the gear in the fake finder window, and delete the backup.
 
Yes, Time Machine is not meant to be a "I backed up my computer two weeks ago, then did another backup today" kind of tech.

Time Machine is designed to run all the time, constantly backing up things bit by bit. If you only plug it in once in a while, the backups will be big, as it's backing up EVERYTHING your computer does in that time frame. Even when I'm just sitting surfing the web and not doing any file work of any sort, the hourly backup might be 20MB or something, as it backs up various things the browser does or the computer itself might be doing in the background. It's not just if you go edit a Word file or download some new porn.

Hard drives are cheap. I'd really suggest getting a 500gb Hard drive and using that instead of the 50GB you say you are using. Then you can have proper TM backups and not have to deal with this keeping track of them. I've had a Time Capsule doing backups for a couple of years and have never touched those backups. Out of sight, out of mind...until I need a file.
 
Guys, I could not find where you can delete previous backups. Where is it exactly??

Also, the idea is that, and this is a good example, I left the mac ON while I went to bed. Woke up next day to find 12 folders of different backups with a timestamp on each. Well, honestly I don't want at some point to have 3000 folders and it would take me forever to read their times and another forever to search through them. Thats not my idea of backups. I want for example 2 folders of a backup I made this week and for example 2 weeks ago, thats it! Thats why its important for me to delete all these backup folders I don't really need!
 
macmba said:
Woke up next day to find 12 folders of different backups with a timestamp on each. Well, honestly I don't want at some point to have 3000 folders and it would take me forever to read their times and another forever to search through them.
Click to expand...

Okay, I think there's some confusion here in terms of what Time Machine does and how you use it. TM saves hourly backups from the past day, daily backups for the past month, and weekly backups for everything older than a month. It's a differential backup, so it isn't like you have a full system copy on a weekly basis.

To use a TimeMachine backup, you go to the TimeMachine icon Applications, or use the Time Machine icon in certain applications.

You *don't* go directly to the backup drive.

See Mac 101: Time Machine for a good overview, specifically scroll down to the "Restoring files from Time Machine Backups" section.
 
deeddawg said:
Okay, I think there's some confusion here in terms of what Time Machine does and how you use it. TM saves hourly backups from the past day, daily backups for the past month, and weekly backups for everything older than a month. It's a differential backup, so it isn't like you have a full system copy on a weekly basis.

To use a TimeMachine backup, you go to the TimeMachine icon Applications, or use the Time Machine icon in certain applications.

You *don't* go directly to the backup drive.

See Mac 101: Time Machine for a good overview, specifically scroll down to the "Restoring files from Time Machine Backups" section.
Click to expand...

I think there is a misunderstanding. I did one backup last night, and I fell asleep, this morning I found something like 10 different backup folders, all from last night. Well, I wanna delete all of them except the first one taken, so I don't have 10,000 folders laying around in the future.. How do I do that?
 
It sounds like time machine isn't for you. Maybe cloning your drive on a regular basis would be better.
 
macmba said:
I think there is a misunderstanding. I did one backup last night, and I fell asleep, this morning I found something like 10 different backup folders, all from last night. Well, I wanna delete all of them except the first one taken, so I don't have 10,000 folders laying around in the future.. How do I do that?
Click to expand...

Ok, let's try this again.

The reason why there were ten backups this morning is because...

deedawg said:
TM saves hourly backups from the past day, daily backups for the past month, and weekly backups for everything older than a month. It's a differential backup, so it isn't like you have a full system copy on a weekly basis.
Click to expand...

So those ten backups were created, one per hour hour, for each hour you were asleep.

Now, since very little will have changed in those ten hours that you were sleeping (unless you had downloads going on, and were backing up the downloads folder), those backups will be quite small - maybe a few meg. You don't need to worry about deleting them as they're taking up very little space.

And, don't forget, those ten folders will go away tomorrow, as tomorrow isn't today. You'll have new folders tomorrow, of course, but they'll go away too.

However, if you really only want to have very occasional backups, TM isn't for you - not the way it's intended to work, anyway. TM is meant as a set-it-and-forget-it service that backs up everything constantly. If you want to only do occasional backups, then look at either a different product (such as Carbon Copy Cloner) or check outTime Machine Scheduler which gives you more control over how and when TM runs.
 
xpipe said:
It sounds like time machine isn't for you. Maybe cloning your drive on a regular basis would be better.
Click to expand...

Agreed.

macmba: Sounds like what you're looking for is the older style "every couple weeks when you remember it" type of snapshot backup -- you'll need to find a different program for that, as Time Machine doesn't work that way.

Time Machine is intended to be a continuous backup, almost like a journaling setup. Thus it will create lots of folders -- like you saw, it did hourly backups of any changes in the previous hour -- you won't hit 10000 folders likely as hourlies are only kept for the previous 24 hrs, then it's daily for a month, then weekly to the beginning.

Since you're supposed to use the Time Machine interface and not go directly to the folders, the actual structure and quantity of folders is irrelevant.
 
Thanks guys. The only way I could see myself using the TM is the following: Turn ON TM, do my backup, and then turn it OFF right after that. Do the same for the next backup, OR just erase the old backup and do a newer one right before the new backup. I honestly need only ONE backup or two at any one time. The point of that backup is if the laptop is stolen, or in case of a hardware crash, or in case i have to service my mBA in which case I will get another MBA, and so on.

I would not mind using another apps for my backups, but I would need something that preferably encrypts the backup, and that is compatible with MAC. What would you recommend?
 
I guess it works like subversions. make sure you understand how subversions or equavelent backup systems work before you do anything to it.
 
macmba said:
I honestly need only ONE backup or two at any one time. The point of that backup is if the laptop is stolen, or in case of a hardware crash, or in case i have to service my mBA in which case I will get another MBA, and so on.
Click to expand...

In my case, I use an old desktop system sitting in the basement as network storage with a 300GB partition dedicated for Time Machine backups. Time Machine manages its files and will delete the older stuff to make room for the new. It is literally set and forget.

If my MBA gets stolen/lost/whatever then I can recover as part of the setup of the new machine. Literally as part of the new machine setup you point it at the Time Machine backup and it restores your files and apps. Again, simple and easy.

The whole point here is it just works without having to mess with it. I don't need to remember to do a new backup every couple weeks. I don't worry about folders or files.
 
deeddawg said:
In my case, I use an old desktop system sitting in the basement as network storage with a 300GB partition dedicated for Time Machine backups. Time Machine manages its files and will delete the older stuff to make room for the new. It is literally set and forget.

If my MBA gets stolen/lost/whatever then I can recover as part of the setup of the new machine. Literally as part of the new machine setup you point it at the Time Machine backup and it restores your files and apps. Again, simple and easy.

The whole point here is it just works without having to mess with it. I don't need to remember to do a new backup every couple weeks. I don't worry about folders or files.
Click to expand...

I see what you mean. But I also hope that your HDD will last if the TM keeps writing on it around the clock: not really my preference if you ask me.

Also, I just noticed that if I am using a say 500GB HDD, and I partition it in ANY way, I cannot encrypt the backup unless its only through 1 partition for the whole drive. I don't understand why. So If I wanted to use 200GB for my MAC backups and 300GB for NTFS for my windows machines, not possible.

I think am just gonna use the TM with the turn ON/OFF switch and call it a day.
 
macmba said:
Thanks guys. The only way I could see myself using the TM is the following: Turn ON TM, do my backup, and then turn it OFF right after that. Do the same for the next backup, OR just erase the old backup and do a newer one right before the new backup. I honestly need only ONE backup or two at any one time. The point of that backup is if the laptop is stolen, or in case of a hardware crash, or in case i have to service my mBA in which case I will get another MBA, and so on.

I would not mind using another apps for my backups, but I would need something that preferably encrypts the backup, and that is compatible with MAC. What would you recommend?
Click to expand...

I think it is a mistake to delete folders... as you may be compromising the integrity of your backup.

Personally... I like the versioning aspect of Time Machine quite a bit. I've been in situations where I have a file (ex: a spreadsheet that I update daily)... where I have noticed that I had made a fatal error the previous day. With Time Machine... I could go back a day or two to get the last "un-compromised" version and then apply the latest changes.

/Jim
 
macmba said:
I see what you mean. But I also hope that your HDD will last if the TM keeps writing on it around the clock: not really my preference if you ask me.
Click to expand...

Thanks, but I'm not really concerned; it's a 3.5" drive in a mid-size tower in a cool room so no heat dissipation issues. Considering the usual life of a primary hard drive, this TimeMachine usage (writing a few dozen meg to it once an hour typically) is minimal load.

My problem is that hard drives generally become functionally useless long before they wear out or die. Not a lot of use for 40G & 80G 2.5" IDE drives or 120G & 160G 3.5" IDE drives, etc. :D

I think am just gonna use the TM with the turn ON/OFF switch and call it a day.
Click to expand...

You might also look at Carbon Copy Cloner as another option, possibly better fitting your intended usage model than Time Machine.
 
Yeah, Time Machine is most definitely not for you if you want to backup that way.

I don't get where you are seeing all these "folders". My Time Machine backup as been going for years, and I only see the single .sparsebundle file. I've never opened it to see what's inside, so maybe that's what you are doing?? Where are you seeing multiple folders??

Your time machine backup will not create tons and tons of full backups. Hourly, it writes backups of only what has changed. At the end of the day, it keeps those changes and forgets about the hourly backups. It keeps those daily backups until it no longer needs those. And so on.

A Time Machine backup almost always has every change of a file made recently. This has helped me on numerous occasions if I accidentally overwrite a big file I was working on two days ago. I just go back and get it the previous version. If you only backup every couple of weeks, this option is gone. I feel safe knowing that all of my work files are backed up constantly. And that would have saved me the last time my hard drive crashed right after one of my busiest weeks ever (and I lost a lot of work). Now I don't have to worry about that.

If I need to access a backup file, I just go into the Time Machine app, navigate to the file I want from whatever day I want, and click "Restore". You are doing all this searching in the Finder? No wonder you are confused. That's not how the backups work.

I think you are not understanding how it works, and are scared that you are going to end up with thousands of folders to sift through. Time Machine is a set it and forget it backup. I have NEVER even paid attention to it in the years it's been running, yet everything I do is backed up all the time. My entire backup after all these years is 316GB for my whole laptop.

But, how you want to do it is your deal. Time Machine is not meant or designed for once-every-two-week backups. I'd really suggest you find something else if that's what you want to do.
 
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