iMac stops recognizing external drive

[davidra]

2012 iMac, fusion drive. Had a Porsche LaCie drive partitioned to Time Machine and the other half for Carbon Copy Cloner. All of a sudden today it won't recognize the drive. It is running, makes the usual boot up sound when it starts up, but isn't seen by the computer....except if you go to the USB device tree. It shows up there, both partitions, but won't show up as a connected drive in Finder or on the desktop. Another thing....if it is connected and running, Disk Utility won't open; it's looking for drives. As soon as I turn it off, the utility opens. It also doesn't show up on my wife's iMac so my assumption is the drive is hosed in some way. Meanwhile I have no Time Machine. I've tried different USB ports, rebooting the iMac....is there anything I am missing? And why is it showing up, with all the information, on the USB device tree if it is not recognized??

 

[tjwilliams25]

It sounds like the drive housing is still operating normally, which would be why it's showing up in the USB tree. Are you able to see the drive in Disk Utility? It may be having trouble mounting.

 

[davidra]

No. If it is connected and running, Disk Utility won't open; it is searching for disks. As soon as I shut off the drive, Disk Utility opens showing all the other drives.

 

[tjwilliams25]

Interesting... The only thing I can think of in that situation is that the drive is trying to mount and having an issue which is causing Disk Utility to hang. Does LaCie have a drive utility? I've used the one that Western Digital has to diagnose drive problems before.

 

[davidra]

There is a manager but it doesn't see the drive. I found a bit of info somewhere else: there is a utility called "fsck_hfs". Apparently that tried to automatically fix the drive before Disk Utility can open it. When I stopped that process, both partitions appeared. I tried to run First Aid on them. Both partitions gave the message "could not be repaired. Try to back up contents of drive". Doesn't sound good to me.

 

[Fishrrman]

OP:

From the looks of post 5 above, you got the drive to mount up again, is this correct?

What I would do next:
- use ANOTHER drive (partitioned) to re-create a ™ backup and CCC backup.
- re-initialize the LaCie drive (just one partition for now)
- next, use Disk Utility's "repair disk" function on it -- do you get a good report?
- if so, REPEAT the repair disk function FIVE MORE TIMES
- do you get a good report each and every time?
- if so, I'd consider the drive ok for regular use.

 

[davidra]

I kept running First Aid. After several times it repaired one partition, which I could then mount. I kept trying with the second partition and after several times it was able to repair that one. I then erased both, repartitioned it, and put Time Machine on one and Carbon Copy Cloner on the other and ran both. Seemed to work OK. I have run First Aid on both of them since reloading and it's showing no errors. But I do have a question. If I re-partition them, is that the same as reformatting them? I notice there is no option for just "reformat".

 

[Fishrrman]

Modern drives do not require "low level" re-formatting.
It's possible to do this, but you need special software. I don't even think there are any Mac-specific utilities that can do this at the "end user" level.

(There -are- Linux and possibly Windows apps that can).

On the Mac, "re-initialization" should be enough.