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Time Machine on a Laptop

D

dvkid

macrumors regular
Original poster
Feb 18, 2006
178
89
It is my understanding per the explanation of the guy at the Apple Store that when you disconnect your Time Machine drive your computer's hard drive is used to temporarily store backups until that drive is reconnected. The length of time you could go on with this being effective is directly related to the amount of free space you have on your internal drive.

In my case, being that my MacBook Pro is not always at my desk, the time between backups could be up to 12 hours (excluding being on vacation).

My plan is to take a bunch of the Apple Loops for Soundtrack Pro and video source files and particle systems for Final Cut Studio and dump them onto a 160 GB external bus powered drive (OWC Mercury On The Go from macsales.com). I also use that same external drive to capture video onto and store my render files.

As my Time Machine drive I'll use a 750 GB Mercury drive connected via FireWire 800 each night. I would also like to find a way to backup my external 160 GB. Ideally it would work like Time Machine. But is Time Machine only capable of backing up what's on the primary OS drive?
 
dvkid said:
It is my understanding per the explanation of the guy at the Apple Store that when you disconnect your Time Machine drive your computer's hard drive is used to temporarily store backups until that drive is reconnected. The length of time you could go on with this being effective is directly related to the amount of free space you have on your internal drive.
Click to expand...

This is incorrect. While you are disconnected, time machine continues to keep track of all files that have changed. When you reconnect they are backed up, but you only get one backup per file, not multiple backups for files that may have changed multiple times while you were disconnected.
 
dvkid said:
It is my understanding per the explanation of the guy at the Apple Store that when you disconnect your Time Machine drive your computer's hard drive is used to temporarily store backups until that drive is reconnected. The length of time you could go on with this being effective is directly related to the amount of free space you have on your internal drive.
Click to expand...
Time Machine receives notifications from the OS whenever a file is created, changed, or deleted. It is my understanding that those notifications are saved until the next time Time Machine runs, either on it's regular schedule or when the Time Machine volume becomes available.
As my Time Machine drive I'll use a 750 GB Mercury drive connected via FireWire 800 each night. I would also like to find a way to backup my external 160 GB. Ideally it would work like Time Machine. But is Time Machine only capable of backing up what's on the primary OS drive?
Click to expand...
Time Machine backs up everything, except for system caches and temp files, unless you tell it to exclude items. That includes external drives.
 
LMO said:
Time Machine receives notifications from the OS whenever a file is created, changed, or deleted. It is my understanding that those notifications are saved until the next time Time Machine runs, either on it's regular schedule or when the Time Machine volume becomes available.
Click to expand...

I believe it receives notifications only when it polls FSEvents for changes. So TM asks what directories have changed since the last time it asked, then it compares each directory to the last backup to see what files have changed, and backs up those files. (Just quibbling with the "whenever a file is created, changed, or deleted" language).

Anyway, the result is the same: when you plug a drive in, TM can find out what files have changed since the last backup, and back those up. If you change a single file 10 times while unplugged from the external drive, TM doesn't keep track of the 10 changes. It only knows that the file is different, and you get a single backup when you plug back in.

Also, while unplugged, no space is used (beyond the normal FSEvents log) for backups. Again, the files are not actually backed up while you are unplugged. All that happens is that a log file keeps track of the fact that a directory changed (not even that a file changed - it's done on the directory level).
 
LMO said:
Time Machine backs up everything, except for system caches and temp files, unless you tell it to exclude items. That includes external drives.
Click to expand...

Ok, great. So I'll just plug in all the externals I need to backup each time I'm at my desk and all should be well. Might even put them on a FireWire hub so I only have to plug in one cable. Hmm...Finally a backup plan that is easy to maintain.
 
my mac HD turns into the Time Mchine drive after I disconnect my external drive. how do I make sure time machein backs up to the external after iconnect and not to my internal?
 
Hard-Hat-Mac said:
my mac HD turns into the Time Mchine drive after I disconnect my external drive. how do I make sure time machein backs up to the external after iconnect and not to my internal?
Click to expand...

What is giving you the impression its using your internal drive?
 
dvkid said:
As my Time Machine drive I'll use a 750 GB Mercury drive connected via FireWire 800 each night. I would also like to find a way to backup my external 160 GB. Ideally it would work like Time Machine. But is Time Machine only capable of backing up what's on the primary OS drive?
Click to expand...

Time machine backs up my main iMac drive and one other external I have connected to it. So it can back up more then the primary OS drive. :) :apple:
 
Hard-Hat-Mac said:
My internal HD "Macintosh HD" they both have the time machine drive icon.
Click to expand...

Ok, I don't know what you are saying (does anyone else?), but I'm pretty sure you are misinterpreting things. Time machine isn't going to use your internal drive for backups.
 
my internal HD has this logo
timemachine_hdicon20071016.png


And so does my G-Drive which I enabled time machine on.
 
coorspate said:
mine is doing the same thing. dont know why.
Click to expand...

I think it means "this drive is backed up in time machine." (and when it appears on an external drive, "this drive is the target of time machine backups.")

People aren't sure if it is a bug or if it is intentional. In any event, it is not copying files TO your internal disk, despite the icon.
 
cmaier said:
I think it means "this drive is backed up in time machine." (and when it appears on an external drive, "this drive is the target of time machine backups.")

People aren't sure if it is a bug or if it is intentional.
Click to expand...

I think that this is actually a more general bug in the Leopard finder. For a while, the Finder displayed the Adobe Bridge icon for a partition on my external drive. After a reboot, it displays the correct icon.
 
cmaier said:
I think it means "this drive is backed up in time machine." (and when it appears on an external drive, "this drive is the target of time machine backups.")

People aren't sure if it is a bug or if it is intentional. In any event, it is not copying files TO your internal disk, despite the icon.
Click to expand...

hmmm that would make sense. It's just not a normal sight is all. I like my old school metal HD drive icon.
 
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