We generate more data every day than at any other time in history, and most of it is stored on hard drives (HDDs) or SSDs for future use. While most of the time that data is safely stored, there are multiple scenarios where even the best NAS drives can fail, not to mention accidental deletion by users. When that happens, there are various ways to recover or restore the missing data, with varying levels of success. It's important to know that professional data recovery is also expensive. If the software-based methods fail, the costs go up substantially, as hardware repair or reconstruction is a tricky task.

What is hard drive data reconstruction or recovery?

Whether accident or virus, you can often find that missing data

Even when you aren't able to read data on a hard drive, most of the time the data is still there, it's just that the operating system can't find the pointers it needs to read the data files properly. Viruses and malware can cause this, as can physical damage or even formatting the drive. The data is still there, but the file table that tells the OS where to start looking is gone. Recovery tools use several tricks to reconstruct the data, like looking for the byte pattern that known filetypes use, and then looking for the next starting pattern to know where to look between.

The software tries to recover files, filenames, and folder structures so that it can reconstruct the drive's contents. You can also attempt RAW recovery, which complicates things as each file type uses a different internal structure, which could be as complex as the file system of the overall drive. It's not quite as simple as clicking a button and letting the program work things out; it often requires manual intervention called "carving." This requires extensive knowledge of how files are structured, as the parts of a file to be recovered could be in multiple locations on the drive.

Things get even more complex if there is a hardware failure or damage. Professional data recovery labs will take the drive into a dust-free clean room and transplant things like the drive platters into another identical drive to get it working long enough to create a full copy of the drive, or other such physical repairs. Then, they run the same software tools and manual processes to reconstruct the data from the copy.

How does SSD data recovery differ?

Data stored on an SSD has no moving parts, but the electronic components are trickier to repair or read from the raw data. Data can be pulled back off the memory chips by addressing the SSD's controller directly, but this is often the component that fails and leaves the drive unreadable. Sometimes, the drive's firmware glitches, and replacing or repairing the firmware allows the drive to be read, but this requires an expert understanding of the SSD's architecture.

You might think that reading the data straight off the memory chips would work, and you'd almost be right except for one feature. The drive's wear-leveling algorithms distribute data evenly across the memory chips, increasing the SSD's longevity. This means individual files could be spread across multiple chips, complicating any recovery attempts. Professional-level tools can reassemble files, but the process is quite involved, and it takes experience to know what is good data and what is bogus.

What if you can't mount your hard drive or SSD?

How do you recover your data if you can't see the drive?

If you've got a hard drive or SSD that won't mount on your system, the first thing to check is the physical connections. Whatever operating system your computer uses, the physical hardware will be similar. Check the power cable (if it has one), make sure any SATA cables are firmly secured, and check the USB cable and connection if it's an external drive. Pay attention to the hum of movement in the drive (if it's an HDD), or any indicator lights on the external enclosure. Also, try a second computer to see if the drive shows up there. If the external enclosure can be opened, you can also attempt to carefully remove the drive to try direct access with internal SATA cables, which works on some enclosures like the LaCie but not so well on WD MyBook drives as those often need the 3.3V pin on the power connector covering before another computer can access them.

Mac users have bigger issues if they can't see their only internal storage, but for external drives, they'll want to look in the Finder settings to make sure external drives are allowed to be displayed on the desktop. Disk Utility can fix many storage issues, including drives not showing up correctly, so try running the First Aid function on the drive in question.

What tools or programs can you use to recover data

You've got options, both free and paid

Before opening any recovery software, try to clone the drive first if possible. Suitable tools include HDDSuperClone and ddrescue, which will completely clone the drive onto another disk. Then you can attempt recovery from the clone, not from the original drive. That gives you a data set that isn't the original, just in case. However, this may not be possible, depending on the status of your drive.

While some well-known tools can recover deleted files, professionals use different programs. Most of the widely-available tools are ones that you can pay for, but affordable ones can be bought for relatively nothing. It's worth mentioning that you should run the demo/trial version of any of these tools before paying for a license. They will all show you a list of the files they can recover and even let you view them to verify the reconstruction was successful. What they won't do is let you save the recovered files without paying, but you can usually pay the nominal fee and upgrade to the full version without restarting the process with the tool.

File Scavenger was developed by a broad group of recovery specialists who use it daily. It's a relatively simple program that produces good results. UFS Explorer is a go-to for many professionals, but it requires more knowledge, so perhaps it isn't the best choice for a first try. Other good tools include R-Studio, GetDataBack, and DMDE, but these are pro-level tools that require some practice to learn how to use.

If you are trying to restore deleted files, the other thing to check is if the app you deleted files from has a recycle bin or trash, which keeps deleted files for some days before deleting them. Apps such as Apple's Photos app have a Recently Deleted folder that stores deleted photos for 30 days so that you can reconstruct your data anytime. This is becoming more common for apps and operating systems, but sometimes, you must know where to find the files you wish to restore.

Sometimes, hard drive data recovery is best left to the professionals

While the software available to home users might manage to recover some hard drive data after issues like accidental deletion, it doesn't always work. If you really need that data, it's time to look up a professional data restoration company, but be warned it'll be expensive.

Also, for future data protection, keep in mind the 3-2-1 data storage rule which says you should have important data stored in three locations, in two different types of media, and one off-site backup. To get started with that, setting up a home NAS gets you most of the way, but you'll want to look into backup providers like Backblaze as well.