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Hi,

I plan to purchase a new Macbook Air and would hesitate to pay $200 more to double the SSD from 128GB to 256. I wonder how much free disk space available apart from what OS X has taken in a new machine. I'm a researcher who does quite a bit of data crunching. But I can live with a 1TB USB3.0 portable HDD. Thanks.

A new Mac with the OS and iLife and iWork apps installed uses abut 20GB of space.
 
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