Late 2012 iMac with 3TB fusion drive failing. Cant boot my bootcamp partition

Sepultura

macrumors regular
Original poster
Jul 10, 2013
155
1
The fusion drive in my late 2012 is failing. Disk utility on OS X shows the flash and mechanical drives as healthy, but i ran DriveDx a few months ago and it reported 59 uncorrectable errors. I have been monitoring SMART with Crystaldiskinfo on my windows partition and its steadily increased. Last week it showed 800 uncorrectable sectors. I was unable to restart windows or even reboot to OS X . Eventually I got back into OS X and it's been running fine for 2 weeks. Disk utility still shows the drives as healthy . I tried windows again today and it locked up as the starting Windows screen. Then I did multiple hard restaets and it says no bootable devices found. I just managed to get startup repair going on a lucky restart and will leave it over night but I expect it to freeze .

For those asking why I'm trying to get into windows . Time machine does not back up the windows partition. I also wanted to check Crystaldiskinfo one last time . I know it's the mechanical portion failing. The flash is healthy .

Hopefully i can get back into os X. I have time machine backups but im worried about the integrity's of the data .

Should i split the fusions drives? I already ordered a 1TB SSD to use as osx and make the 128gb internal for bootcamp. It's a shame this Macs are a pita to disassemble .
 

Fishrrman

macrumors P6
Feb 20, 2009
17,385
5,622
If you're sure it's the HDD portion of the fusion drive, I'd try this:

1. BACK UP (I -always- recommend a bootable cloned backup created with CarbonCopyCloner, which is free to download and use for 30 days).

2. Boot from your cloned backup drive.

3. Use terminal to "DE-fuse" the fusion drive into standalone HDD and SSD

4. Use Disk Utility to erase and test the SSD.

5. Use Disk Utility to erase and test the HDD.

6. Put your OS, apps and a "bare-bones" user account on the SSD (by bare bones, I mean that you should not include the large libraries in the home folder, which are normally documents, music, movies, and photos.
The idea is to keep the SSD "lean and clean", so it will at its best.

7. IF the HDD tests ok (again using Disk Utility, run the repair disk function on it about 5 times in succession), you could keep the large libraries on the HDD.

Now your OS and apps are on the fast internal SSD, and the Mac will boot and run faster than ever.

Keep BOTH drives backed up (again, I recommend CCC or SuperDuper).

That's how I'd do it.
 

Sepultura

macrumors regular
Original poster
Jul 10, 2013
155
1
Do a complete Time Machine backup now
I already have a Time Machine backup from yesterday. I am worried if any of the data is corrupted though. Time Machine only backups the latest changes, but I have no way knowing if the lastest stuff copied is clean.

If you're sure it's the HDD portion of the fusion drive, I'd try this:

1. BACK UP (I -always- recommend a bootable cloned backup created with CarbonCopyCloner, which is free to download and use for 30 days).

2. Boot from your cloned backup drive.

3. Use terminal to "DE-fuse" the fusion drive into standalone HDD and SSD

4. Use Disk Utility to erase and test the SSD.

5. Use Disk Utility to erase and test the HDD.

6. Put your OS, apps and a "bare-bones" user account on the SSD (by bare bones, I mean that you should not include the large libraries in the home folder, which are normally documents, music, movies, and photos.
The idea is to keep the SSD "lean and clean", so it will at its best.

7. IF the HDD tests ok (again using Disk Utility, run the repair disk function on it about 5 times in succession), you could keep the large libraries on the HDD.

Now your OS and apps are on the fast internal SSD, and the Mac will boot and run faster than ever.

Keep BOTH drives backed up (again, I recommend CCC or SuperDuper).

That's how I'd do it.
I plan to use an external SSD as the boot drive. I will use the internal flash storage as a Bootcamp partition from now on. I guess I can't split the fusion drive right now because CarbonCopyCloner would only backup the flash storage partition.