Time Machine

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Hello all, i have 2 questions about time machine today.

1. How much space does it use to back up?--does it get larger and larger as you put more stuff in your drive to back up, or does it allocate a certain amount then fill it?

2. Is it possible to backup 2 different macs on the same external drive?


Thanks in advanced for your help,

GF
 
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Your Mac's Specs
White MacBook Intel C2D 2.2GHz, 2G, 250G, SD, Leopard.
Hello all, i have 2 questions about time machine today.

1. How much space does it use to back up?--does it get larger and larger as you put more stuff in your drive to back up, or does it allocate a certain amount then fill it?

2. Is it possible to backup 2 different macs on the same external drive?


Thanks in advanced for your help,

GF
1. TM backs up everything and maintains archives of your system over time. In theory, your backup system will grow over time until it is full. At that point, you should change your backup drive.

My internal hard drive is 250G. My backup, an internal hard disk in an external drive box, is a 500G drive. I figure I'm good for at least 6 months and probably a year. (Realistically it's probably longer than that, but I like to be conservative on such estimates.)

2. You could probably do that if you want, but I wouldn't recommend it. Whatever drive you have should probably be 2x the total drive space between the two machines. If you try this, you'll have to experiment to see how well Leopard maintains archives for the two machines.

One issue I see is that you are depending on one drive to backup two systems. If that drive fails, you're potentially in trouble. Backups for both systems are lost at that point, and you are no longer protected against failures of your machines.

Another issue I see is that you cannot connect your backup drive to both machines at the same time. To backup both machines, you'll need to regularly switch your external drive between both machines. At some point you'll probably stop doing it, unless the machines are typically side-by-side.

Apple suggests you not use your backup drive for storing other files, so using one drive to backup two machines is probably a Bad Thing. My guess is that you can do it, but it's not a good idea.

My recommendation would be to have a separate backup drive for each system. This reduces the likelihood of losing all of your backups, and helps to ensure you'll maintain good backups for both systems.

Hope this helps!
 
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godfatherrr
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well my original plan was to have an iMac always hooked up, and then whenever i got the chance, plug up a macbook and have that seperatly backed up. but you have turned me off to that so its all irrelevant ;)

anyway, as i understand it TM backs up the image of your harddrive for that time, then the same thing the next day, then the next day, and when it runs out of space, it can just delete the oldest image. Is this correct?
 
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15" Unibody MBP 2.4 Ghz C2D, 2 GB RAM, 250 GB HDD, 320 GB Time Machine HDD, 1 TB Ext Media Drive
Anyway, as i understand it TM backs up the image of your harddrive for that time, then the same thing the next day, then the next day, and when it runs out of space, it can just delete the oldest image. Is this correct?

Time Machine is a little bit smarter about backing up your internal drive than most people give it credit for.

What happens is the FIRST time Time Machine runs, it creates a mirror image of your internal drive. This takes the longest of all the backups.

After this backup, Time Machine examines your internal drive every hour that your computer is turned on. It polls the recent changes to your drive. If any files have a NEWER timestamp than the last time Time Machine examined the drive, it stamps that file, and backs it up to the external drive.

This is where it gets tricky...Time Machine keeps a log of all the files it backs up, where it stores different versions of files as you change them and it backs them up, and at what time each file was backed up between changes/adding/removing files, etc.

In essence, once Time Machine backs up your drive for the FIRST time, your backup external (or internal) drive will fill up MUCH SLOWER than it did with the first backup. Unless you are in the habit of downloading or storing HUGE files on your internal drive, your Time Machine backup drive will fill a lot slower than you think.
 

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