Problem reading iMac HD

[Rain]

Hi!

I just returned from a week-long congress. I left my computer (a 27" iMac from 2009 or so) running a super-heavy Mathematica code on three of its four cores (can't recall whether they're i5 or i7 cores, but I doubt that's relevant). When I came back, I tried to wake the computer up by pressing a random key on the keyboard. The screen turned on (although it was black), but the "enter password" prompt did not appear. I moved the mouse around and could see the cursor moving across the screen, but still nothing. The fans and hard disk were not spinning, so I figured the computer had run out of memory and disk space due to Mathematica and turned it off by pressing the power button for a few seconds. According to my mother, who stayed at home and accidentally pressed a key on the keyboard while dusting my room this morning, the "enter password" prompt came up, so up until a few hours ago everything was just fine.

I turned the computer back on, but it didn't get past the white screen that comes up before the Apple logo and the spinning gear appear. I turned it back off (via the power button) and on a few times, but every time I'd get the same thing. If I leave it a while longer, the Apple logo and the spinning gear come up, but the computer stays like that forever (about half an hour straight so far).

I then tried botting the computer in "safe mode" (shift) (also pressed command and V to get info), but nothing happened. I plugged it into my mother's Apple laptop and booted it as a target disk; the laptop could see it (although it took an awful lot of time to read it), but when I opened my iMac's hard drive the window was empty. Eventually a few icon placeholders and folder names came up, but I couldn't interact with anything in it (as soon as I clicked on something, the spinning beachball of death appeared and I had to force-restart the laptop). I don't remember what exactly was there, but the usual folders (System, Applications, Users) were present; I also remember seeing a handful of icons I'm not familiar with, most notably a file called "youtube.html".

So far, these are the conclusions I've reached:

1. It's not a memory problem, since rebooting should clear the RAM (all 8 GB of it) and the computer would have booted normally from the first try.

2. It's not a peripheral problem, since I tried disconnecting everything (except the keyboard and the mouse, although the mouse is the wireless Apple mouse that connects to the computer via BlueTooth) and the problem is still there.

3. It probably has to do with some unreadable file in the hard drive, but the only thing that could possibly be there that wasn't there before I left for the congress is some enormous Mathematica temporary file filling up every last kB of disk space and this isn't the case (pressing command+i on my iMac's hard drive when it was a target disk on the laptop revealed that 600+ GB (out of 1 TB) are free/unused, just as before I left; I can't think of anything else that could have appeared, since Mathematica was the only thing running (beside the Finder and probably the Dashboard widgets) when I left a week ago.

I know for a fact that nobody could have accessed the computer and dont anything to it because it's password-protected and there are no guest accounts or anything.

In case it helps, I'm running Mavericks (I updated two days after it came out) and my version of Mathematica is 9 (which had previously run flawlessly).

Thanks for any help!

 

[oldscribe]

Hi,

I am not a user of Mathematica but spoke to a friend who is and there reply was as follows.
There are two implementations of the standard C++ library available on OS X: libstdc++ and libc++. They are not binary compatible and libMLi3 requires libstdc++.

On 10.8 and earlier libstdc++ is chosen by default, on 10.9 libc++ is chosen by default. So to ensure compatibility with libMLi3,you will need to choose libstdc++ manually.

To do this, add -stdlib=libstdc++ to the linking command.
Sorry that my only input.

 

[Rain]

Hi, oldscribe. Thanks for the help, but compatibility with Mathematica shouldn't be the issue at work here. I've worked with Mathematica 9 for months and had no compatibility problem. At any rate, I can't add that line until my computer boots up.

 

[Kaveman]

I'm running Mavericks (I updated two days after it came out) and my version of Mathematica is 9

New OS and old software, I think you need to check the Mathematica site for updates and to see if there are other issues.

 

[Rain]

Thanks, Kaveman. Again, though, I doubt my issue is compatibility; I've used Mathematica 9 since it came out, and a compatibility issue shouldn't prevent my computer from booting up, just from running Mathematica.

Really, my question isn't about how to prevent this from ever happening again; it's about what to do given that it just happened. And I can't prevent anything from happening until I fix my computer anyway.

 

[oldscribe]

Hi,

Did you make a Mavericks bootable USB drive prior to upgrading?if so use that. Personally feel this is a must before upgrading.
If not have you have tried using the original install disks.

 

[Rain]

No, I just upgraded. In retrospect, I probably shouldn't have.

I have install disks for OS 10.1; I'm sure I have disks for 10.6 as well, but I need to find them.

I'm pretty sure it's a problem with the HD. I tried booting it as a target disk again, and any interaction with it takes ages; also, I get error -50 whenever I try to delete something (which makes no sense, since it's formatted as Mac OS X extended journaled and Mathematica doesn't seem to have created a horrendously large temporary file with some ridiculous name involving symbols at the high end of the ASCII spectrum).

 

[oldscribe]

Hi,

I tried booting it as a target disk again, and any interaction with it takes ages;

Maybe install the drive in external caddy and access.
But if you can't find disks I would book a GB appointment, could be HD or a plethora of things, have to say if HD I would possibly expect to see a question mark. But then again anything can happen with technology no matter how advanced.
Please keep us posted.

 

[Rain]

I ended up taking it to the Mac Store, and they said the drive was physically damaged (so yes, nothing to be done except replace it). It was horrendously expensive and took a week and a half (no appropriate HDs in stock, gah), but little damage was done -- Time Machine and TimeMachineEditor are the best inventions since, er, the wheel. Or fire. Or language.

New HD's working as any new piece of technology should. =)

Thanks for everything!

 

[Morhass]

Hi Rain

I turned the computer back on, but it didn't get past the white screen that comes up before the Apple logo and the spinning gear appear. I turned it back off (via the power button) and on a few times, but every time I'd get the same thing. If I leave it a while longer, the Apple logo and the spinning gear come up, but the computer stays like that forever (about half an hour straight so far).​

As far as I can see, here's your big clue… when the spinning gear comes up under the Apple logo, the Mac has loaded just enough of the software to see there's a need to run its self-repair… unfortunately, when you get to fsck by that method, it doesn't give you any feedback… the fact that it takes a while before getting that far is a concern.

I'm hoping that, given you've just done a major upgrade, you have a good backup - data loss is now a distinct possibility!

You have a couple of options at this point…
- seeing as you're already familiar with using another computer and bringing it up in T mode, start there - on the other computer, run Disk Utility and repair. The advantage of doing it through Disk Utility is that you get more readable feedback than other methods…

- alternatively, start up the iMac with the option key down to enter startup manager, and start of your Mavericks recovery disk… again, run disk utility… my guess is that it will try and reinstall f the OS to replace files that are damaged… depending on whether the problem is hardware or software, this may not help...

 

[Rain]

I'm hoping that, given you've just done a major upgrade, you have a good backup - data loss is now a distinct possibility!

Yes, I run daily backups with Time Machine and TimeMachineEditor and also have my most important stuff in DropBox.

- seeing as you're already familiar with using another computer and bringing it up in T mode, start there - on the other computer, run Disk Utility and repair. The advantage of doing it through Disk Utility is that you get more readable feedback than other methods…

I tried verifying, repairing and erasing/formatting. No matter which of those options I chose, Disk Utility returned a "cannot unmount disk" or similar error (after trying for quite a while and succeeding at other tasks) every time. I ended up replacing the hard disk.

- alternatively, start up the iMac with the option key down to enter startup manager, and start of your Mavericks recovery disk… again, run disk utility… my guess is that it will try and reinstall f the OS to replace files that are damaged… depending on whether the problem is hardware or software, this may not help...

The person at the Mac Store tried that, but he couldn't boot even from external disks with various OSs (Snow Leopard, Lion, Mavericks).

In the end, he mentioned that the disk had taken physical damage somehow (which I already suspected).