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mac does not see external hard drive

my mac does not see my external hard drive

iMac, OS X Mountain Lion (10.8.1)

Posted on Sep 4, 2012 12:17 PM

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90 replies

Oct 31, 2013 2:43 PM in response to Lilian M.

Is that the only copy of that valuable data, on that one external drive? Or does it also exist on another computer that you own?


If that external drive has the only copy, do you still have the Windows PC (or other Mac) where it worked before? If you do, does the hard drive still mount properly using one of those systems? If it does, I would use that computer to transfer the data to another portable drive. Before using that second drive, connect it to the MacBook Air to make sure it is fully accessible (you can read and write data on the drive).


If you want in-person assistance, and there is an Apple Store nearby, you may want to make a reservation with the Apple tech support folks at the store's Genius Bar. If the data also exists on another computer, and that computer is portable, you should bring it along, in addition to the external drive, because it may be possible to set up a direct computer-to-computer network connection.


Otherwise, you can try doing a Repair Disk. Normally, it will do no harm to try it. A simple problem will be fixed, but Apple keeps the Verify and Repair commands separate for a reason. Repair Disk may alter the data while trying to repair, and may make the problem worse if not successful. I did not want to suggest you do it, if that is the only copy of the data, and you have other options.

Nov 10, 2013 5:32 PM in response to Kenichi Watanabe

Just reading through this thread as I have an external hard drive that was working with my MacBook Air, but has recently stopped working. I'm afraid the drive itself has been damaged (probably by my children tripping on the wire). The drive is not showing up under Disk Utility. Is there any hope other than sending my drive off for data recovery? I'm really hoping I can do something as finances are tight here and I'd really rather not have to send my drive away. Any ideas??? Thank you in advance.

Nov 10, 2013 9:38 PM in response to Calicommando

You should do a few things to confirm the Mac's USB port is working properly. Shut down (power off) the Mac. Disconnect all USB devices, including USB hub if you use one. Since this is a MacBook, connect its power adapter (so that it's not running on battery power). If the external hard drive has its own power switch, turn it OFF. If it has its own power supply, disconnect it.


Start up the Mac. Turn ON the external drive and connect it to a direct USB port on the Mac.


If that does not help, connect something else to the USB port, to confirm it's working, preferably something similar like another external drive, or maybe an iPod/iPhone/iPad (if you have one), or a USB flash drive. Something that would be recognized as a "disk" by the Mac.


You should also rule out a faulty USB cable as the cause, by trying a different cable.

Nov 17, 2013 7:53 PM in response to PAL1963

I"m having a similar weird issue. My Firewire 800 HDD suddenly stopped working while connected to my mac air with thunderbolt to FW800. Tried it on my iMac with just firewire 800 pluged in daisy chain on another HDD. still didn't work.. tried it daisy chained on my Mac Pro via G Tech GSafe.. works just fine and reliable. plug it back into the Air or theiMac.. still doesn't work.... weirrrrrrdddddddd....


Disk Untility on iMac and Air don't show it, and everything appears normal on Mac Pro...


thinking of getting some Esata cables.. maybe the Esata are more reliable than FW800?

Nov 17, 2013 8:16 PM in response to pixelator123

Is this a 3.5-inch external drive that has its own power supply, or a 2.5-inch "portable" drive that gets power from the FireWire connection?


What about the "other" FireWire 800 drive connected to the iMac, to which it was daisy-chained (3.5" or 2.5")?


What happens if you connect it directly to the iMac's FireWire 800 port?


When connected to the MacBook Air, be sure to connect its power adapter (so that it's not running on battery power).

Dec 19, 2013 11:10 AM in response to Martyn4950

You should rule out possible causes. Is this a USB drive, or another type, such as FireWire?


First, shut down (power off) the Mac, not just restart. To isolate the problem, disconnect other devices (including any hub), except for standard keyboard and mouse (if used). Also power off the external drive, if it's the type that has its own power supply. Then, start up the Mac and connect only the external drive to a direct port on the Mac.


If that does not make a difference, connect something else (preferably something that is a storage device like another external drive or flash drive or iPod) to the same port to confirm the port works properly.


To rule out a bad cable, try another cable, or try the cable you were using with another device. If it's USB, make sure you are not using an old cable from the days before USB 2.0.


If you have ruled out the port and the cable as causes, the most likely cause is a problem with the hard drive (either on the external case or the hard drive mechanism itself).

Dec 19, 2013 12:23 PM in response to Martyn4950

It's possible that the problem is the external case, and not the hard drive inside (unless you are hearing odd noises like clicking or whining), so you may want take the case apart and try the hard drive separately. You can do that with another case, or with an "adapter" (which is really a case without the case). OWC sells one


http://eshop.macsales.com/item/NewerTech/U3NVSPATA/

Dec 20, 2013 1:54 AM in response to Kenichi Watanabe

Taking the case off does nothing new, because it is still connected to the case's interface. Quite often, the problem is the case, not the hard drive inside. The hard drive mechanism is a precision part, usually of high quality. The quality of the case (and its interface) varies greatly, depending on the "cheapness" of the manufacturer. If you bought the cheapest external drive you could find, the case is where the vendor "went cheap" (not the hard drive). If your data is really valuable, isn't it worth the time and expense to check if the hard drive is still working?


Also, as a Mac user, you should use the built-in Time Machine to automatically back up your personal data. ALL hard drives eventually fail. With Time Machine, you set it and forget it, until you need it because your next hard drive failed. Then, you have a backup that is automatically up to date, to within one hour of failure (when the Mac is in use and the Time Machine archive drive is connected). Plus, you have an ongoing archive where you can retrieve files (and emails/contacts) that you erased by mistake, including older versions of files.

mac does not see external hard drive

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