MacBook air ssd space

uba2012 said:

Does the MacBook air or any other Mac make system images like Windows. (like reverting back to another time).

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Not on the disk itself, you can configure Time Machine on an external drive, Time Capsule or Time-Machine compatible NAS

If you specifically want System Images as one file you can use the SuperDuper! App. It has a good following. I use Time Machine as default and use SuperDuper! every few months or so.

SpoekGTi said:

Not on the disk itself, you can configure Time Machine on an external drive, Time Capsule or Time-Machine compatible NAS

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Time Machine in Lion is configured by default to store its snapshots on the same disk when that external one isn't available. When that one because available it moves the local snapshots to the external TM drive.

This seems a bit stupid because you have backups on the same media and device as you are backing up. That is not a proper backup but it does have an advantage. Because TM backups very regularly (hourly) you can easily restore a file you messed up or deleted accidentally. It won't protect you against things like theft, a crashing disk, etc. The only problem is that it takes up space and doesn't really show you. There is a way of disabling these local snapshots. For that you need to get to the commandline by firing up Terminal (iTerm2 is a highly recommended alternative to that) and typing the command: tmutil disablelocal. If you want it back all you have to do is type tmutil enablelocal. Disabling the local snapshots will save you some diskspace which is ideal with the 64GB and 128GB ssd options.