How does Time Machine work?

[sanford]

I presume the distance Time Machine will go back in time is dependent on the size of external hard drive you have? As in, equal space is required for the full clone, but the more over that you have the further you can go "back in time" to restore incremental conditions.

I think Time Machine is very neat, but I've almost decided against using it. I have a 160GB external for back-ups, which well covers the important bits on my 120GB notebook internal, and I just don't feel like spending even a measly $100 for a larger capacity Time Machine drive. I use .mac Backup and although people have issues with it, it's always worked for me, and I've never ever ever done any kind of incremental restore. I've only used my back-ups twice, both in the case of catastrophic drive failure, in which case they saved my bacon; but in 20+ years of Mac use, I've never accidentally deleted a file or photo I needed or wanted. An e-mail or two, yeah, but typically I catch it soon enough to dig it out of the trash mailbox; or nothing so serious I haven't been able just fire off a "Can you resend blah blah blah?"

 

[garethlewis2]

Well, and your point being?

You don't want to use Time Machine for backups, good for you. There will be people who have been praying for a feature in OS X like this. Maybe without all the eye-candy.

When reading your post and putting it through the Raymond Chen filter, it comes back as, "I don't do anything interesting, and if I deleted everything, it wouldn't matter"

 

[sanford]

Well, and your point being?

You don't want to use Time Machine for backups, good for you. There will be people who have been praying for a feature in OS X like this. Maybe without all the eye-candy.

When reading your post and putting it through the Raymond Chen filter, it comes back as, "I don't do anything interesting, and if I deleted everything, it wouldn't matter"

Wow, gareth, dick much?

My principal point was the question about exactly how size of back-up media influences how far back you can go in Time Machine. I stated at the outset that Time Machine is a very cool solution, but perhaps just not for me.

As for doing interesting things, I said I didn't accidentally delete important things, not that I didn't do important things or that if I lost it them all it wouldn't matter. Indeed in those two cases of catastrophic drive failure my back-ups were invaluable. I'm sure Time Machine will be a boon to you in keeping ready at hand all your pre-prepared, generic, ass-face forum responses when, surfing porn blind drunk on Thunderbird one night (every night?), you accidentally delete them to make extra room for all those MILF mpegs you bought with your grandmother's Visa number.

Take a piss, gareth.

 

[Deej]

I think Sanford's got a point though - has anybody stopped to consider exactly how much storage Time Machine is going to require over time?

So you take some photos on holiday, come back and put them into iPhoto (which stores the originals as well as any changes), and they get backed up. Any changes you make (I suppose) will also get backed up.

Now your music - what if you have a 10Gb music partition - maybe you edit some of the meta info associated with an mp3. That all gets backed up.

Now extrapolate that over a year or two, and how much storage are we all actually going to need?

 

[scotthayes]

I'm pulling up a chair and getting ready for this little fight...

Back to your corners, on the sound of the bell come out fighting, no punching below the belt.


DING DING - Round 1

 

[Much Ado]

There was a YouTube clip of Scott Forstall explaining this at WWDC, which i shall now try to find.

Here we are. Does this help? http://www.youtube.com/watch?v=X2OPprfi3Dk

 

[edesignuk]

Now extrapolate that over a year or two, and how much storage are we all actually going to need?

Time Machine deletes the oldest copies of files as and when more space is required for new files.

 

[Deej]

Time Machine deletes the oldest copies of files as and when more space is required for new files.

Thanks - that's all well and good (and it is good that it does that), but size the external disk too small and it'll just end up overwriting backups you may need to return to at a future point, if that makes sense..

 

[hobbbz]

TM backs up once fully, then only the changed files after that. So if you have a 120GB main HD (completely full) and a 160GB backup you will then have all 120GB backed up and 40GB left over for changes. That is, if you change <40GB of data, your backup drive will not fill up. I will assume you are not running your 120GB drive at full capacity though so that leaves considerably more room for backups. You can also tell TM to limit the amount of space it uses and which folders to back up so it will only keep as much backup as you have allowed.

 

[sanford]

I think Sanford's got a point though - has anybody stopped to consider exactly how much storage Time Machine is going to require over time?

So you take some photos on holiday, come back and put them into iPhoto (which stores the originals as well as any changes), and they get backed up. Any changes you make (I suppose) will also get backed up.

Now your music - what if you have a 10Gb music partition - maybe you edit some of the meta info associated with an mp3. That all gets backed up.

Now extrapolate that over a year or two, and how much storage are we all actually going to need?

Yeah, deej, thanks. I'm not whining about it. I'm just curious. Time Machine is obviously going to have to cut off somewhere due to space available. I mean, over a couple years, with MP4 video and MP3/AAC music, we're talking maybe a terabyte, more, because let's say you have a bunch of MP4 DVD rips you made for vacation to carry on an iPod, when you get back you delete them and you *mean* to delete them because you have the DVDs at home; it's going to track all those, and do it again every time you do something temporary like that. Sure a terabyte is much cheaper than it used to be, but still, that's a lot of space for the average user using Time Machine to back up an off-the-bat three-quarters full 80GB notebook drive, but said user doesn't actually ever stay much over three-quarters full for long.

 

[Deej]

TM backs up once fully, then only the changed files after that. So if you have a 120GB main HD (completely full) and a 160GB backup you will then have all 120GB backed up and 40GB left over for changes. That is, if you change <40GB of data, your backup drive will not fill up. I will assume you are not running your 120GB drive at full capacity though so that leaves considerably more room for backups. You can also tell TM to limit the amount of space it uses and which folders to back up so it will only keep as much backup as you have allowed.

Makes sense... I assume it only backs up user data and not the OS / Applications?

 

[iBlue]

A solution to the problem I read a few posts up is to do those temporary things with time machine OFF. That way when you intentionally delete your movies/music it won't be holding that back-up when you do. Turn it back on accordingly.

Thanks - that's all well and good (and it is good that it does that), but size the external disk too small and it'll just end up overwriting backups you may need to return to at a future point, if that makes sense..

Of course. But that's like getting angry that the iPod shuffle you bought won't hold all your music. I think I see a way out of this.

 

[hobbbz]

I believe it does everything by default. Including apps, Library, etc. The point being you can fully restore a machine from a TM backup.

 

[sanford]

TM backs up once fully, then only the changed files after that. So if you have a 120GB main HD (completely full) and a 160GB backup you will then have all 120GB backed up and 40GB left over for changes. That is, if you change <40GB of data, your backup drive will not fill up. I will assume you are not running your 120GB drive at full capacity though so that leaves considerably more room for backups. You can also tell TM to limit the amount of space it uses and which folders to back up so it will only keep as much backup as you have allowed.

Oh my God, hobbbz? Useful answers to a legitimate questions. Get the hell off these forums. You obviously don't belong here. Ban hobbbz! Ban hobbbz!

Seriously, brother, thanks. With that level of flexibility in managing back-ups via Time Machine, I will almost surely give it a try at least. And, yeah, I'm a writer, so although I have a bunch of space in iTunes and CD-ripped music, about 5GB of family photos and such, my actual work files are tiny and out of approx. 111GB formatted capacity of a 120GB drive, I have approx. 59GB free right now. So 160GB will likely serve me a while, and as you said I can cap it at a certain point so any giant files I briefly have and then intentionally delete will just go away, not push me to buy more storage any time soon.

 

[Littleodie914]

I believe it does everything by default. Including apps, Library, etc. The point being you can fully restore a machine from a TM backup.

Yep, but you can add/remove locations that you *don't* want TM to backup, much like you can add/remove the locations Spotlight searches through.

 

[sanford]

A solution to the problem I read a few posts up is to do those temporary things with time machine OFF. That way when you intentionally delete your movies/music it won't be holding that back up when you do. Turn it back on accordingly.


Of course. But that's like getting angry that the iPod shuffle you bought won't hold all your music. I think I see a way out of this.

Ooh, Blue, good idea. And for deej, yeah, it clones the whole puppy then tracks changes. So you could reformat and and do a full reinstall at the last automatic state save, or install in a larger drive and just put the whole deal back on the new drive.

I'm going to at least try it, as it sounds like it will always safely keep the bulk of my important data, being work, photos of the kids, and music I guess so I wouldn't have to re-rip everything in a drive-failure scenario. If I hate it I can also just wipe the TM drive and go back to using my .mac Backup sets.

Update: Hmm. Like you could nix apps and all the system stuff from the TM back-up, which essentially gives me the same deal now but in a perhaps more convenient, pretty package. Say, what about using any spare space left on the back-up drive. Like what if I use it for TM, but also want a folder on there to store DVD rips offline of my main HDD that I don't want to keep all the time because I'll just play the DVDs, but might want to stick back in iTunes for a trip? Can I just create that folder on the TM drive and it will effect is the amount of space TM has available to back up?

Update update: Actually the above question is even more pertinent because contrary to gareth's comments I'm actually rather freaky about backing up, especially photos of the kids and whole drafts of books on which I'm working. If you can stick other stuff on the TM drive besides TM stuff, then I could keep using .mac Backup to do my big back-up set to the same drive, for a while until I'm comfortable with TM and it doesn't make me nervous it'll "intelligently" lose something for me.

 

[elppa]

This is the best explanation I have seen to date:
http://www.appleinsider.com/articles/07/10/12/road_to_mac_os_x_leopard_time_machine.html&page=2

 

[Deej]

All positive stuff

However, thinking of non-technical home users out there (some of whom I have the pleasure of supporting ), it sounds like it could be quite complex to set up to get the best use out of the storage available

I can already see the conversations in the future:

"you ran out of space so TM overwrote the backup that we now need"

"but you told me a 250Gb would be more than sufficient"

"I know, I'm sorry, but actually you need to buy a bigger disk now"

 

[iBlue]

Is there no way to prioritize items in there? Say command it to never delete iPhoto libraries and things like this. (?)

I imagine it warns you before deleting things, right?

(honestly asking, I'm not sure)

 

[Markleshark]

All looks good.

Can I tell Time Machine, for example, not to backup my iTunes Library?

 

[Project]

All looks good.

Can I tell Time Machine, for example, not to backup my iTunes Library?

Yes

 

[Markleshark]

Yes

Sweet, thanks.

 

[atszyman]

Yeah, deej, thanks. I'm not whining about it. I'm just curious. Time Machine is obviously going to have to cut off somewhere due to space available. I mean, over a couple years, with MP4 video and MP3/AAC music, we're talking maybe a terabyte, more, because let's say you have a bunch of MP4 DVD rips you made for vacation to carry on an iPod, when you get back you delete them and you *mean* to delete them because you have the DVDs at home; it's going to track all those, and do it again every time you do something temporary like that. Sure a terabyte is much cheaper than it used to be, but still, that's a lot of space for the average user using Time Machine to back up an off-the-bat three-quarters full 80GB notebook drive, but said user doesn't actually ever stay much over three-quarters full for long.

But Time Machine does not hold the information forever. The DVD rips will get backed up the first time they are seen. Then over the course of the next few months, if you do a lot of DVD ripping, TM will run into either the back up drive hard limit or the artificial limit that you set. TM will then start to delete the oldest files that are no longer on your computer. If you haven't deleted anything other than the DVD rips TM will eliminate those.

Another idea would be to create a folder for the DVD rips or whatever other temporary files you have and tell TM not to back up that folder.

The TM backup isn't going to stop working because you run out of space, it will simply limit the amount of time you can trace back in the past. If you currently do your own, daily, weekly, monthly backup then you probably just take a snapshot of your HD at that time, giving you no recourse to go back any further than that point in time. If you're only doing weekly or monthly backups you also run the potential for losing up to a week's or month's worth of data if you have a hardware failure, where if you manage to remember to plug in an external drive every night or so you can limit your losses to only a day, less if it's a static machine always connected to an external drive.

I don't currently have an external HFS drive but TM is making it very tempting. Maybe I'll buy a couple of 120s or 160s and update my PowerBook HD and create an external as well. I have, in the past been pretty good about backing up my laptop on a weekly basis to my PC at home (mirrored RAID), with a monthly backup of that PC to an external drive. I do however miss weeks and months sometimes so TM would be an extra, or more consistent backup solution as a first level.

 

[sanford]

But Time Machine does not hold the information forever. The DVD rips will get backed up the first time they are seen. Then over the course of the next few months, if you do a lot of DVD ripping, TM will run into either the back up drive hard limit or the artificial limit that you set. TM will then start to delete the oldest files that are no longer on your computer. If you haven't deleted anything other than the DVD rips TM will eliminate those.

Another idea would be to create a folder for the DVD rips or whatever other temporary files you have and tell TM not to back up that folder.

The TM backup isn't going to stop working because you run out of space, it will simply limit the amount of time you can trace back in the past. If you currently do your own, daily, weekly, monthly backup then you probably just take a snapshot of your HD at that time, giving you no recourse to go back any further than that point in time. If you're only doing weekly or monthly backups you also run the potential for losing up to a week's or month's worth of data if you have a hardware failure, where if you manage to remember to plug in an external drive every night or so you can limit your losses to only a day, less if it's a static machine always connected to an external drive.

I don't currently have an external HFS drive but TM is making it very tempting. Maybe I'll buy a couple of 120s or 160s and update my PowerBook HD and create an external as well. I have, in the past been pretty good about backing up my laptop on a weekly basis to my PC at home (mirrored RAID), with a monthly backup of that PC to an external drive. I do however miss weeks and months sometimes so TM would be an extra, or more consistent backup solution as a first level.

I back up daily work files to .mac, but of course that can't hold my iTunes library or all my photos and what have you. Then I back up all important data "as needed" to an external drive, like when I buy iTunes music, or offload photos from our camera -- works out to about every week, but of course I skip sometimes, too. But it would be awfully convenient to just plug 160GB USB2 drive into my laptop every night and let it do its thing, not actually thinking about running Backup and when I really need to run Backup, etc. And since my main concern is *current* back-ups, not going back in time to fetch something I accidentally deleted or deleted thinking I wouldn't need it again, 160GB is going to more than sufficient, even if I do a whole mirror of the drive including apps and system and all the other stuff that's easy to reinstall from disc. I'll probably have space left over on that 160GB for storing this or that, too.

Yeah, I'm definitely going to give TM a shot. Merely switching on and plugging in that external drive every day, I'll be daily current on at least a single full back-up without any hassle. That's pretty cool right there.

 

[BornAgainMac]

I am worried it won't work

I have my iTunes library and iPhoto library on a 500 GB external drive. I know TM will backup my Macbook Pro's 160 GB drive to an external drive. But I don't know how I'll backup my external data drive to another external drive. I want to keep my Macbook Pro's backup separate from my external data drive backup.

The main reason to separate them is because I actually have 6 external drives with data with 6 external drives to manually backup those drives.

I might need Time Machine Pro if such a product could exist.