We generate more data every day than ever before in history, and most of it is stored on hard disk drives (HDDs) or SSDs for later use. While most of the time the data is safely stored, there are several scenarios where even the best NAS drives can fail, not to mention accidental deletion by users. In this case, there are several ways to recover or restore the missing data, with varying degrees of success. It is important to note that professional data recovery is also expensive. When the software-based methods fail, the cost increases significantly, as repairing or reconstructing the hardware is a difficult task.
What is hard drive data reconstruction or recovery?
Whether accident or virus, you often find missing data
Even if you can't read data on a hard drive, most of the time the data is still there. The operating system just 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 operating system where to start looking is gone. Recovery tools use various tricks to reconstruct the data. For example, they look for the byte pattern that known file types use, then look for the next starting pattern to know where in between to look.
The software will attempt to recover files, file names, and folder structures so it can reconstruct the contents of the drive. You can also attempt a RAW recovery, which complicates things because each file type uses a different internal structure that can be as complex as the entire drive's file system. It's not quite as simple as clicking a button and letting the program do the work; it often requires manual intervention called “carving.” This requires extensive knowledge of the structure of files because the parts of a file to be recovered may be located in multiple places on the drive.
Things get even more complicated when 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 make it functional long enough to make a complete copy of the drive or perform other such physical repairs. They then run the same software tools and manual processes to reconstruct the data from the copy.
What is the difference between SSD data recovery?
Data stored on an SSD has no moving parts, but the electronic components are harder to repair or read from the raw data. Data can be recovered from the memory chips by addressing the SSD's controller directly, but this is often the component that fails and renders the drive unreadable. Sometimes there are bugs in the drive's firmware and by replacing or repairing the firmware the drive can be read, but this requires expert knowledge of the SSD's architecture.
You might think that reading the data directly from the memory chips would work, and you'd be almost right, except for one peculiarity. The drive's wear-leveling algorithms distribute the data evenly across the memory chips, increasing the SSD's lifespan. This means that individual files could be scattered across multiple chips, making any recovery attempts difficult. Professional tools can reassemble files, but the process is quite complicated and it takes experience to know which data is good and which is fake.
What if you can't mount your hard drive or SSD?
How can you recover your data if you can't see the drive?
If you have a hard drive or SSD that won't mount in your system, the first thing you should do is check the physical connections. No matter what operating system your computer is using, the physical hardware will be similar. Check the power cable (if you have one), make sure all SATA cables are firmly connected, and check the USB cable and connection if it's an external drive. Listen for the sound of the drive moving (if it's a hard drive) 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 try carefully removing the drive to test direct access with internal SATA cables. This works with some enclosures like the LaCie, but not so well with WD MyBook drives, as they often require the 3.3V pin on the power connector cover before another computer can access it.
Mac users have bigger problems when they can't see their only internal storage, but for external drives, they should check Finder preferences to see if external drives are allowed to appear on the desktop. Disk Utility can fix many storage problems, including drives not showing up correctly, so try running the First Aid feature on the drive in question.
You have options, both free and paid
If your data is valuable or irreplaceable, contact a professional before attempting DIY methods. If your data loss had a physical cause, attempting to recover the data yourself could further damage the physical hard drive, making later recovery less likely. Some signs of a physically damaged hard drive include strange noises such as clicking, scratching, or loud screeching (in the case of a hard drive), or slow performance, missing files, messages such as “drive not found,” and frequent overheating. If you notice these signs, it's best to leave data recovery to a professional.
Before opening any recovery software, try to clone the drive if possible. Suitable tools are HDDSuperClone and ddrescue, which clone the drive completely to another hard drive. Then you can try to perform the recovery from the clone, not the original drive. This way you will have a data set that is not the original, just in case. However, depending on the status of your drive, this may not be possible.
While some well-known tools can recover deleted files, professionals use other programs. Most of the commonly available tools are paid, but more affordable tools are available relatively cheaply. It's worth noting that you should run the demo/trial version of any of these tools before paying for a license. They all show you a list of the files they can recover and even let you view them to check if the recovery was successful. What they don't do is let you save the recovered files for free, but you can usually pay the small fee and upgrade to the full version without having to restart the process with the tool.
File Scavenger was developed by a large group of recovery specialists who use it on a daily basis. It is a relatively simple program that produces good results. UFS Explorer is the first choice for many professionals, but it requires more knowledge and therefore may not be the best choice for the first attempt. Other good tools are R-Studio, GetDataBack and DMDE, but these are pro tools that require some practice to use.
Another thing to consider when trying to recover deleted files is whether the app you deleted files from has a recycle bin that keeps deleted files for a few days before deleting them. Apps like Apple's Photos app have a Recently Deleted folder that stores deleted photos for 30 days, so you can always restore your data. This is becoming more common across apps and operating systems, but sometimes you need to know where to find the files you want to recover.
Sometimes data recovery from hard drives is better left to the professionals
Although the software available for home users may be able to recover some hard drive data after problems such as accidental deletion, it doesn't always work. If you really need that data, it's time to find a professional data recovery company. Be warned, though, that it will be expensive.
For future data protection, also consider the 3-2-1 data storage rule, which states that you should store important data in three locations, on two different types of media, and an off-site backup. To start with, setting up a home NAS will be mostly enough for you, but you should also look into backup providers like Backblaze.