Optimal Drive Size, Place – and Time – for Time Machine?

So, a Genius at my local Apple Store recommended that the optimal external drive size for Time Machine should be 2 – 3x the size of my primary drive. My MacBook has a 160 GB drive of which I typically use about 70 to 100 GB, depending on how often I get to move my ODM source files.

My MacBook is my primary machine and I take it home with me every day (and just about every place else I go). If I were to get a 500 GB or 1 TB drive, should I keep it at the office or at work? How often does Time Machine take snapshots of my machine and at what time of day? Continually?

Here’s another scenario: What if I were to get a portable 250 GB drive and carry it with me? It’s not the 2 – 3x capacity recommended by said Genius, but at least I wouldn’t have to worry about where and when to use my drive.

Any ideas for me?


Every hour, every day, an incremental backup of your Mac is made automatically as long as your backup drive is attached to your Mac. Time Machine saves the Time Machine iconhourly backups for the past 24 hours, daily backups for the past month, and weekly backups for everything older than a month. Only files created and then deleted before the next hourly backup will not be included in the long term. Put another way: You’re well covered.

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