iinstalling apps on an external drive

Hi,

I'm buying my MBA 11" soon and am still deliberating on the SSD size.

My preference would be to go 128gb and install all the apps on my old PC onto an external drive. These would be the apps I'd use at home, i.e. software for printers, my GPS device, and install pages on the internal SSD.

I'm assuming that the apps would run fine from the external drive, but if the mac was started up without the drive attached, nothing catastrophic would happen?

My rationale is buying a fast external 500gb drive seems half the price of the 256gb upgrade and will also allow me to plug it into the PC I use for photography if need be at any point later on..

Running applications from an external drive is of course possible but will be slow compared to running them from the internal flash drive. Also consider this: The MBA 11" is small, light, easy to carry around, why defeat that by having to drag an external drive around?

Buy the largest flash drive for the MBA that you can afford. There are after market updates available but they're expensive right now. Prices will come down in the future as more and more notebook computers are equipped with flash drives.

I second chscag's advice. By all means, move your media libraries (which are what really take up significant space) onto an external drive -- but OS X is pretty clearly designed by UNIX standards, and that means all applications should reside in the Applications folder, which is located on the boot drive.

It's certainly POSSIBLE to relocate this stuff, but complicated and fraught with risk. I can't recommend it, particularly as apps tend not to take up a great deal of space on one's boot drive.