Self-ejecting external USB drives

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SystemError51(Posted 2012) [#1]
I'm on OS X Lion 10.7.4 right now. Everything is working perfectly well - except for one thing, and I'm wondering if any of you guys experienced the same issue.

Did it happen to you, that you connect an external drive to the Mac, and regardless of what you do, the drive would spontaneously and mysteriously self-eject?

For me this happens with a SATA-drive I put into an enclosure, which is then connected with USB. In the middle of Time Machine backups, it would just disconnect for no apparent reason. There is no visible pattern to it, and no visible regularity.

I already tried to disable "Put hard disks to sleep if possible" in System Preferences -> Energy Saver, to no avail.

I tried a different USB cable, which for the moment seems to work fine. But I don't know when or if it's gonna do it again.

This seems to be an issue since Snow Leopard - so I'm wondering if anyone has experienced the same, and how you went on about it.

Last edited 2012


GfK(Posted 2012) [#2]
It's most likely that the enclosure you bought and/or the drive, requires more power than the USB port can give it.

The best option is to get an external drive with its own power supply.


ima747(Posted 2012) [#3]
I would put money on the controller in the external enclosure. Those symptoms have usually resolved for me as a failing controller although once it was a power related issue as GFK suggested. Power issues usually (for me) have resulted in a warning dialog that the disk was disconnected improperly followed by the drive re-appearing, but it will of course depend on the drive, the system, etc. etc. Check in order of cost: cable, boost/stabilize power, alternative drive in same enclosure, same drive in alternative enclosure.