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I have a Macbook Air running 10.7.2, with a LaCie external USB drive.

Whenever my external drive is plugged in, my MBA always takes a long time to boot (1-2 mins in grey screen before the Apple and the spinning cycle appear) Usually it boots in less than 20 seconds. If I unplug the drive, the boot process continues as usual (fast).

  • I tested my drive on my iMac and it boots just fine.
  • I tested with HFS+ Journal as well as exFAT, problem persists.
  • I tested with both of the USB ports on my Air, no change.
  • I have already reset PRAM -> no help.
  • I tested both GUID and APM -> ... nth changes.

My guess is the machine is trying to see if the external drive is bootable. How do I prevent this action?

Any ideas?

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In System Preferences>Startup Disk is your internal drive selected? – Samantha Catania Oct 29 '11 at 7:43
@SamanthaCatania yes, it's the only bootable disk appears in there. The external is not-bootable, data only – Tuan Anh Tran Oct 29 '11 at 7:45
Can you test booting your computer with another drive attached to see if the problem is caused by all external hard disks? If you suspect that the problem is your machine checking for bootability of the external drive (even with no system), it would be useful to attach a drive with a system but set startup to your Air. If the system boots from the external anyway something's going on with the system or pram or as you suspect, whatever piece of software is checking bootability of all attached drives. – Richard Oct 29 '11 at 10:41
- the LaCie (without adapter) works on iMac but not MB Air. I'm thinking about maybe it doesnt draw enough power from a single usb port? could that be the problem. – Tuan Anh Tran Oct 29 '11 at 12:20

closed as too localized by bmike♦ Dec 21 '12 at 15:36

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