External disk drives not mounting at boot

Question

Level 2

417 points

External disk drives not mounting at boot

External OWC disk drives attached to my 'mid-2011' 2.7 GHz iMac running 10.7.2 sometimes fail to mount and/or show in the Finder on boot.

Other times they all do. No other phenomena. No other faults once mounted - IOW, they don't ever dismount.

They just fail to show at all (in Disk Utility, for example, etc).

Anyone any idea what could be going on, please? An otherwise perfectly-operating machine.

TIA!

iMac, Mac OS X (10.7.2), Clean machine... no haxies; no Microsoft etc

Posted on Jan 10, 2012 9:19 AM

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Answer 1

baltwo

Level 9

62,362 points

Jan 10, 2012 9:22 AM in response to Mark Sealey

How connected? All mine are FireWire and never fail to connect on boot. If you're using USB, I can't help, since only input devices are hooked up that way.

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Answer 2

Mark Sealey Author

Level 2

417 points

Jan 10, 2012 9:24 AM in response to baltwo

I'm sorry. Should have said.

FireWire and USB. It applies to both buses if it happens at all :-(

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Answer 3

baltwo

Level 9

62,362 points

Jan 10, 2012 12:21 PM in response to Mark Sealey

Thanks for clarifying. Zap the PRAM and Reset the SMC; then, see if that fixes the problem.

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Answer 4

Mark Sealey Author

Level 2

417 points

Jan 10, 2012 12:24 PM in response to baltwo

Thanks. I wondered about that. Would odd/bad values in the PRAM etc account for the intermittent nature of the fault?

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Answer 5

baltwo

Level 9

62,362 points

Jan 10, 2012 12:33 PM in response to Mark Sealey

Don't know, but do know that if the problem continues after resetting those to their default values rules out any odd/bad values.

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Answer 6

Mark Sealey Author

Level 2

417 points

Jan 10, 2012 12:41 PM in response to baltwo

Indeed.

Are we sure that values relating to disc drives are held there?

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Answer 7

Star1

Level 2

465 points

Jan 10, 2012 12:52 PM in response to Mark Sealey

Hi Mark,

I wonder WHY you don't try what baltwo is suggesting instead making a conversation out of it...

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Answer 8

Mark Sealey Author

Level 2

417 points

Jan 10, 2012 12:55 PM in response to Star1

Star1,

Because I'm not at the machine in question now; and am a little nervous about losing all my other settings unless I'm better than 50% certain it'll help.

Thanks :-)

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Answer 9

baltwo

Level 9

62,362 points

Jan 10, 2012 1:07 PM in response to Mark Sealey

Read the linked documents and you'll see what's reset. Do note that most of those are never changed by users.

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Answer 10

Jan 10, 2012 1:17 PM in response to Mark Sealey

I had a similar issue and it was simple to solve. After a reboot, I first had to plug in the A/C Power supply and THEN the FireWire wire.

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Answer 11

Mark Sealey Author

Level 2

417 points

Jan 10, 2012 1:18 PM in response to baltwo

baltwo,

Thanks. Will do!

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Answer 12

Mark Sealey Author

Level 2

417 points

Jan 10, 2012 1:19 PM in response to RioCreations

RioCreations,

Interesting. I wondered: is it best to power up the drives first, or the iMac?

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Answer 13

Jan 10, 2012 1:21 PM in response to Mark Sealey

I don't know but I powered the iMac up and then the A/C Power for the External HD and then the FireWire cable. Problem solved in my case.

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Answer 14

Mark Sealey Author

Level 2

417 points

Jan 10, 2012 1:23 PM in response to RioCreations

Permanently? Or do you have to do that every time?

That's what's odd in my case… weeks will go by with no prob. Then several boots in a row no mounting.

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Answer 15

TheSock

Level 1

14 points

Oct 19, 2012 4:58 PM in response to Mark Sealey

I have the same issue on several of my Mac's. It is particulary bad if I use a WD book drive. I find this anonying because the people using the computer don't realize timemachine is not working and not backuping up there systems. When I come along the drive has not been mounted for weeks. If I simply unplug it and plug it back in it mounts and everything is fine for a few weeks. If you leave the mac running there is no problem because the drive never unmounts. The problem is also seen with a segate drive that powers off the firewire. USB or firewire makes no difference I have different drives with both types of connections. Interesting I have a Nexstar enclosure that doesn't seem to have the problem but I can't be sure cause it happens at random.

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