# Time Machine Speculation



## Qion (Aug 9, 2006)

Well, how do you guys think it works? 

Main problems I forsee: 

1. What happens to those of us with laptops who enjoy disconnecting from external drives when we visit the café or generally move about? If you were to, per se, download an "I'm a Mac." commericial, watch it, and delete it 5 minutes later, would Time Machine still access it? Would Time Machine work at all? 

2. What happens when you are continuously running Time Machine for months on end, and constantly create/delete large files? How would it ever begin to account for the film industry without having gigantic ammounts of storage to feed into? 

3. If you were to, for whatever reason, disconnect from a volume, do a lot of work, and reconnect to that volume, would there be a large pause while Time Machine "automatically" updated? 

My personal opinion is that Time Machine will somehow access "deleted" files from exactly where they were deleted. As some of us know, when you erase something, it doesn't _actually_ go away until something else fills the same sector of space. This would run into problems, however, with conspiracy theorists and their zeroing and people who do not own 1TB hard disks. 

I guess we're just stuck speculating...  

(Oh, and on a completely unrelated tangent, why do you think Steve had two iSights connected to his computer(s)? Back-up system maybe?)


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## Mikuro (Aug 9, 2006)

It seems that Time Machine will not log every little change. It's not a real-time thing like Spotlight. It's more like OS 9's indexing. From Apple's web site:





> Backup Time: Time Machine will back up every night at midnight, unless you select a different time from this menu.


So, once a day (maybe more or less if you can specify it) it will back up all modified files. I doubt it deals with "ghost" space at all.

I really don't know how they're going to deal with large files like video. What happens when the backup disk fills up, as it will inevitably do? Are older backups silently removed to make room? Are new backups ceased? Does it cry like a baby and tell you to buy another HD?


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## Satcomer (Aug 9, 2006)

The big things I see are still unanswered. 

1) What if you don't want to use it, can it be turned off?
2) Will it work with more than just FireWire and USB2 drives? I mean things like raids, external off site servers and things along that line.
3) If someone has an external hard drive and another machine user or another machine access the data?
4) Will it make a boot able clone?
5) Will it back up immediately so if I delete some 10 minutes ago and get it back?
6) Will it only work with HFS+? Will it support other formats? Also will it work with my internal 4 hard drives (in the MacPro)?
7) Can two or more  users use the same backup drive?

There are probably  at least 50 more questions that others have. Also it looks like Apple is stepping on a lot of backup developers toes.


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## powermac (Aug 9, 2006)

Those are great questions. When I read and seen the demonstration it reminded me a bit of my IBM Aptiva I had several years ago. The computer had a program where you could go back and restore files, etc. From what I understand the program only wrote what had changed, not everything. In other words, the system registered a changed in a particular file or folder, and those that had not changed where not written. 
Not sure how Apple is working Time Machine. It does look like it will be a handy app.


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## Ferdinand (Aug 9, 2006)

Time Machine IS the coolest Back-Up App (if thats what I can call it). Even though I dont have a copy of Leopard (I only watched the WWDC from the computer) I think it will blow the Backup app in the dust. Its much simpler than backing up. But: What if the Harddrive breakes, so the files arent accessable anymore. What will Timemachine do? It cant recover anything.

And... why are they bringing it out ONLY in Spring? Why not much eariler like November or October? If they announce it before christmas, then more people will buy it (as a Christmas present). Thats how they selled so many 5th gen iPods.


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## Mikuro (Aug 9, 2006)

Ferdinand said:


> And... why are they bringing it out ONLY in Spring? Why not much eariler like November or October?


I'm guessing the same reason they didn't release it today or in January or the day after Tiger came out: it's not done yet.  As long as they don't pull a Longhorn on us, I won't complain. Personally, I think it was silly of them to announce the name as soon as they did. All it did was get people thinking "Leopard! Leopard!", and now we've been waiting for it for so long (even though it was nothing but a name until Monday) Spring 2007 seems so...far...awayyyyy....

Two years between major releases isn't so bad. Most people feel abused with faster updates. ("They want me to pay again _already?!_")



> 1) What if you don't want to use it, can it be turned off?
> 2) Will it work with more than just FireWire and USB2 drives? I mean things like raids, external off site servers and things along that line.
> 3) If someone has an external hard drive and another machine user or another machine access the data?
> 4) Will it make a boot able clone?
> ...



My guesses:
1. Apple says _"By default, Time Machine backs up your entire system. But you can also select items youd rather not back up."_ I'm guessing this will have an interface similar to Spotlight.

2. Apple stresses "servers" a lot, both in Steve's keynote and the Time Machine page. The TM page only specifies machines running Mac OS X Server. It's hard to say whether servers based on other OSes will work.

3. The backups would probably have the same permissions as the original, in which case it would be the same as trying to access the original from another user/system. Any other way would seem kind of backwards, wouldn't it?

4. I've been wondering this myself. Apple hasn't offered any real clues. They say it will back up _everything_, but they don't really say anything about how it's stored. Booting from backed-up data would cause a lot of complications, though, since it would make the backup out of sync with the original (you can't boot without altering some system files and prefs and stuffs). So my instinct is "no", but I hope I'm wrong.

5. Apparently not. Apple's TM page says it's scheduled, and that by default it backs up every night at midnight. If it logged every little change, that would be impressive, but it would also fill up the backup disk like mad! I don't think anyone really wants to back up every single file that makes its way into their web browser's cache, for instance.

6. My guess is that you can only back up HFS+ drives (since it will probably use Spotlight to determine which files need to be backed up, and Spotlight only supports HFS+). Maybe you'll be able to use other formats for the backup volume, but I doubt it.

7. I would think so, since apparently it's made to use source drive as the backup. It would seem very strange if it TM was limited to just one user on isolated machines (which means the vast majority of consumers, probably).

Of course, it's all just speculation. Even what Apple has said directly is subject to change, as they remind us at the bottom of every page about Leopard.


Last week people were hoping Leopard would be released at MWSF in January. Now it seems more likely that we'll merely get all the details of Leopard in January.


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## chevy (Aug 14, 2006)

On the sneak peeks on Apple web site, it looks like Time Machine is integrated in the applications, as if it was managing the applications' data base. If this is the case, this is completely different from a generic back-up software.

But it also only applies to compatible software.


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## Mikuro (Aug 14, 2006)

All the data from those other apps would be stored in files, so it's possible apps like Address Book just poll Time Machine for the old files, and process those files the same way they process the _current_ files.

But you could be right, and it could be much more sophisticated than that. It seems likely that it would at least make special considerations for the Spotlight database; after all, it would be silly to back up the entire database every day if only 1% of the entries in that database would be any different from the previous day. A Spotlight database could easily be hundreds of megabytes.

It's possible that Time Machine will use temporal compression, storing only what has changed in every day's entry, much the same way a modern video codec only stores what changes between frames. It would be quite a feat to make that work efficiently and flexibly, though. The Address Book test proves that Time Machine needs to be fast enough for programs to perform arbitrary analysis of the old data in close to real time, and any compression scheme would surely take its toll on performance.

I'm sure a lot of people at Apple lost a lot of sleep thinking about all these problems. I reeeeally want to know more about Time Machine's inner workings! But it's fun to speculate.


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## fryke (Aug 14, 2006)

From what I've heard and seen so far, it _is_ a rather generic backup software behind the nice outfit. The integration into the apps is only about _retrieving_ stuff again. Just an interface to the backup's database.


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## chevy (Aug 14, 2006)

It really looks like Apple is considering the complete file system like a big database (probably including the Finder, which explains why all files can be retrieved), but some databases are special, like Mail, ToDo or Calendar databases: their files are made of records and apparently the back-up happens at record level.

Very impressive, probably as efficient as the CVS for large text files systems.


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## progginRay (Aug 16, 2006)

What I don't understand is that things like that are sceduled late at night. A normal person switches off the computer when he/she has doen his/her work. Computers eat lots of electric power, and with laptops it's even harder to leave them on all the time.
Imo it would be more of sense tho scedule back ups or cron scripts before a shut down.


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## ElDiabloConCaca (Aug 16, 2006)

progginRay said:


> What I don't understand is that things like that are sceduled late at night. A normal person switches off the computer when he/she has doen his/her work. Computers eat lots of electric power, and with laptops it's even harder to leave them on all the time.
> Imo it would be more of sense tho scedule back ups or cron scripts before a shut down.


I'm sure that, just like with the "daily," "weekly," and "monthly" cron scripts, they would run at the first occurrence that the machine is awake if the scheduled backup during the night happened to be missed due to the computer being asleep or shut down.

You can verify that this is true with the "daily," "weekly," and "monthly" cron scripts by inspecting their respective log entires with the Console.  On my machine, the times that these scripts are run coincide with the times that I get up in the morning and awaken the machine.  Normally they would run overnight, but since my machine sleeps at night (much like a human), they get run automatically the first chance the computer gets after the missed schedule date.  I would assume that Time Machine would employ a similar scheduling algorithm.

Especially with a laptop, having to wait for Time Machine to back up files when you tell the machine to shut down just wouldn't be feasible.


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## progginRay (Aug 17, 2006)

That's how they do it?
I always had the feeling that my mac was speeding up after running the cron scripts manually, hahaha.
That shows how much computer speed can be a matter of ones mind.


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## Sunnz (Aug 17, 2006)

Mikuro said:


> 5. Apparently not. Apple's TM page says it's scheduled, and that by default it backs up every night at midnight. If it logged every little change, that would be impressive, but it would also fill up the backup disk like mad! I don't think anyone really wants to back up every single file that makes its way into their web browser's cache, for instance.



But, in WWDC, didn't they said something along the lines with, that if you have overwritten your file by clicking save, but you actually wanted to do 'save as', you can 'go back in time' to get your original file?

BTW, there is one thing that the _Time Machine_ couldn't do - the future!! However, I think OSX is ahead of other OS out there anyway!


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## Mikuro (Aug 17, 2006)

Sunnz said:


> But, in WWDC, didn't they said something along the lines with, that if you have overwritten your file by clicking save, but you actually wanted to do 'save as', you can 'go back in time' to get your original file?


Yeah....provided the original file existed at midnight, I suppose. If you accidentally save over a file you just created, I think you're screwed just like in any other OS.

At least, that's what it sounds like from all the info Apple offers. They've never explicitly said any of this. But then again, obviously they're not going to explicitly define the _weaknesses_ of their Great New Thing!

What would be cool is if Time Machine allowed you to specify priorities. So you could tell it, "Only check my library once a day, but check these folders once an hour, and update those folders with every single change." But I don't really expect this.


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## Sunnz (Aug 17, 2006)

Well maybe they can backup the new file as soon as you hit save? I mean, that would be just like a CVS Add & Commit, shouldn't be hard to implement.


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## cybergoober (Aug 18, 2006)

I saw a screen shot somewhere which showed that in addition to scheduled backup times, there was a setting called "Automatically." Perhaps this setting backs up files as they are created/mofified to work like they described in the keynote?


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## lurk (Aug 18, 2006)

I have no NDA and no special info but it was kind of my impression that it did keep track of the thing you just saved so you could go back to it.  Then these were batch copied out later.

They talked about a whole API for interfacing with the thing, so it ought too do more than just run rsync at midnight.

But whadda I know, I just sits in the peanut gallery.


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## SOCOMRAIDER (Aug 19, 2006)

I have a question about Time Machine. 

-Does it *require* Core Animation to work?

If so, does that mean G4 PowerPC Mac mini owners will be without Time Machine? Since only computers that support Core Image will be able to support Core Animation. And the Mac Mini doesn't support Core Image.....

??????


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## sheepguy42 (Sep 2, 2006)

Qion said:


> (Oh, and on a completely unrelated tangent, why do you think Steve had two iSights connected to his computer(s)? Back-up system maybe?)


Yes, always. iSight is a FireWire device; it makes more sense to have a separate one for each system.


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## Sunnz (Oct 29, 2006)

Does anyone know how big does your backup hard drive have to be for Time Machine to work effectively?


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## aicul (Nov 2, 2006)

Sunnz said:


> .. how big does your backup hard drive have to be ..


Is this really a concern at the current sales price of external hard drives?

In my opinion, I would not want timemachine to backup every instant of my mac life. However, a simple backup, say daily, would suit my purpose.

The fact about backups is that they must be EASY, this means I do nothing and can recover a file I saved for over 24hours with ease. 

I consider silly things such as having to connect a hard drive a hassle. I would like timemachine to find the available harddrive I have on wifi and use that one. No fiddling with cables.


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## Sunnz (Nov 2, 2006)

aicul said:


> Is this really a concern at the current sales price of external hard drives?



Yes.

Whenever I get a new hard drive, I tend to quickly fill them up with movies music's and stuff... it gets pretty tricky when you already have several already large hard drives laying around your desk, and now I am gotta to buy a copy for each of them? (Or a really big one that can backup all data I already have... but again, if I can buy such big hard drive, I might buy another and fill it up...)

Well ok, maybe it is my problem... given the price of hard drives these days, I tend to keep a lot of "rubbish", every-time I as about to delete something, I have the feeling of, "I have so much space anyway so I'll just put them somewhere else."


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## aicul (Nov 2, 2006)

> ..  tend to keep a lot of "rubbish", every-time I am about to delete something, I have the feeling of, "I have so much space anyway so I'll just put them somewhere else." ..


I know the very feeling. It's all about the difference between *storing* and *hoarding*. 

Whatever the system, if you have too much data, you have too much data. Which means that recovery, in whatever manner, becomes .. difficult.


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