Extracting Data from a Broken Hard Drive I need to extract data from a Hard Drive of a 2011 MBP that usually won't boot because of a seemingly broken drive. The computer booted on some attempts, but it usually shows a gray question mark logo and holding CMD+R boots internet recovery.

The MBP can be booted through an external USB hard drive with a copy of OS X installed on it, but only the external drive does shows up in Disk Utility.

I think it can be concluded that the main hard drive is damaged. This can further be supported by the fact that the SATA/SATA Express tab in the system report shows Unknown under the first Intel 7 Series Chipset where the Hard Drive is meant to show up. Is there any way to extract data from this hard drive? Are there any special tools necessary? If so, then are they cheaper than bringing the laptop to the service shop?
At this stage it is normally not a job for amateur to extract data from the drive.

If you highly value the data on the drive, I wouldn't recommend bringing it to a standard service shop, as they wouldn't have the means to do anything. I would hire a specialized data recovery company to recover the data.

If you have no such option, one of the cheapest and easiest ways to recover after such a problem is to replace the electronics on the drive. Buy a 100% identical hard drive (new or used), replace the PCB on the old drive with the PCB from the new drive. If this works, copy over your data straight away to a backup drive.

Note: This only fixes some types of disk errors. If for example the drive heads or platters themselves are damaged, replacing the PCB won't help. But it also means that you have to have very special tools and facilities to be able to read data from the drive.