What is Data Recovery for Storage (SSD/HDD)? Mechanism and Recovery Methods Explained

This article explains data recovery in cases where data is accidentally deleted or lost due to storage device failure.

Depending on the situation, it is possible to easily recover data using tools, or if that is not possible, data can be restored by a professional service for a fee.

This article also explains the mechanism behind data recovery, including why deleted data can sometimes be restored.

Depending on the cause of data loss, it may be easy to recover the data, so it is important to be careful when disposing of storage devices.

This article also covers basic knowledge about storage standards and popular storage configurations, as well as how to choose storage from the perspectives of performance and compatibility.

≫ Related Article: How to Choose Storage (SSD/HDD) for Custom PCs [Performance / Features / Compatibility]

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What is Data Recovery for Storage Devices (SSD/HDD)?

Data recovery for storage devices refers to the technology and methods used to restore lost data from storage devices such as SSDs and HDDs.

There are two main causes of data loss: logical failures and physical failures.

Logical failures are caused by accidentally deleting files, formatting drives, virus infections, or file system corruption.

On the other hand, physical failures are caused by hardware problems such as SSD or HDD malfunction, dropping, water damage, or component wear due to aging.

There are many reasons for data loss, and the appropriate recovery method depends on the type of failure.

The main data recovery methods are using recovery tools or requesting help from a professional service.

Recovery tools can handle logical failures by scanning the storage device and listing recoverable data, allowing the user to restore the necessary files.

This method is relatively inexpensive and easy to use even for those who are not familiar with computers, but it cannot be used if the storage device is physically damaged.

On the other hand, requesting help from a professional service is effective when there is physical damage or advanced logical failure.

However, the cost can range from tens of thousands to hundreds of thousands of yen, and for RAID configurations or servers, it can be even higher. Therefore, it is important to choose based on the importance of the data and the available budget.

When attempting data recovery, it is important to prevent data from being overwritten.

Therefore, as soon as data is lost, stop using the device and start the recovery process.

Neither method guarantees that data can be fully and completely recovered. The possibility of recovery depends on the cause of data loss, the time elapsed, and the condition of the storage device.

Therefore, when handling important data, data recovery should be considered a last resort, and regular backups should be performed.

How Data Deletion and Recovery Work on Storage Devices (SSD/HDD)

This section explains how storage devices save and delete data.

Normal File Deletion Does Not Erase Data

When files are deleted normally, they disappear from Windows and cannot be accessed, but the data is not actually deleted from the storage device.

“Normal file deletion” refers to the following actions:

• Selecting a file and deleting it with right-click or the Delete key
• Right-clicking the Recycle Bin and choosing “Empty Recycle Bin”
• Deleting data inside the Recycle Bin (permanent deletion)
• Deleting with the Shift key held down for permanent deletion

Generally, when a file is deleted, it is moved to the Recycle Bin and can be restored if needed.

When deleting from the Recycle Bin, a prompt asks, “Do you want to permanently delete this file?” and the file can be deleted from the Recycle Bin as well.

Also, by holding down the Shift key while deleting, files can be permanently deleted without passing through the Recycle Bin.

Here, “permanent deletion” means that the file is deleted in Windows, making it invisible and inaccessible to the user.

However, in reality, the area of the storage device where the file was saved is only marked as “free space,” and the data remains on the storage device.

Therefore, using recovery tools, it is possible to restore such files.

Here is why this happens.

Storage devices use file systems to manage where and how data is stored.

When managing data, metadata (index/directory entries) is kept to manage the physical location, size, and attributes of each file in addition to the actual file data.

When a file is deleted in Windows, only the metadata (index/directory entry) is marked as “free space,” while the actual data remains on the storage device.

When users perform file operations, Windows refers to the file system metadata to locate the physical storage location of the specified file.

After locating it, Windows reads the actual data from the storage device and provides it to the user.

However, when the metadata is marked as “free space,” Windows treats the file as nonexistent, making it invisible (as if deleted) to the user.

In other words, normal file deletion only makes the file invisible and inaccessible in Windows, but the data remains on the storage device.

Data is Deleted by Overwriting the Same Area

It was explained that normal file deletion does not erase the data, which may raise the following questions:

• Why is it designed this way?
• When is the data actually deleted from the storage device?

This is a design for efficient file management. In reality, data is deleted from the storage device when new data is written to the same physical area as the deleted file.

This design speeds up the file deletion process and also helps extend the lifespan of the storage device.

Deleting a file from storage means deleting it by overwriting the data.

Computer data consists of 0s and 1s, and when deleting actual data, the area is overwritten with all 0s to erase the file.

In other words, deletion also involves a write process, just like saving a file.

Therefore, if only the appearance of deletion is needed, it is enough to overwrite the area when a new file is saved.

If the system were designed to physically erase data at the time of deletion, there would be two write operations: one at deletion and one at saving a new file.

In either case, the user gets the same result when accessing files, so reducing the number of write operations reduces the load on the storage device and extends its lifespan.

Also, when deleting or saving a large number of files at once, limiting the process to apparent deletion reduces write operations and improves overall efficiency.

For these reasons, when a user deletes a file, only the metadata is updated, and the actual data remains on the storage device.

Data Before Overwriting Can Be Recovered

Actual data deletion occurs when new data is written to the same physical area as the deleted file, so until then, the data remains.

Therefore, data can be recovered until it is completely deleted.

Data recovery tools can scan for such remaining data and restore it.

Therefore, if a file is accidentally deleted, it may be possible to recover it using a data recovery tool.

However, if new data is overwritten, recovery becomes difficult, so if data is lost, stop using the computer immediately and start the recovery process.

Some may think, “I won’t create or save any files, so it’s fine,” but file creation and saving are not only done by users. The system may perform such operations in the background, so it is best to stop using the device and start recovery as soon as possible.

About Disposing of Storage Devices

If personal information such as names, addresses, photos, videos, account information, or credit card information or highly confidential files that should not be leaked are stored on a device, make sure to “completely” delete the data before disposal.

Be especially careful when selling to second-hand shops.

As mentioned earlier, normal data deletion leaves data on the storage device, making it possible to recover. If someone buys the device second-hand, they may be able to recover the data, leading to information leaks.

There are two main ways to dispose of storage devices:

• Use a data erasure tool
• Physically destroy the storage device

Using a data erasure tool overwrites the data so it cannot be recovered.

What these tools do is overwrite the data one to three times with meaningless data (such as 0000).

This completely deletes all data.

Physically destroying the storage device involves drilling holes in the hard disk or smashing it with a hammer.

Doing this yourself can be difficult and dangerous due to flying metal or glass fragments, so it is better to use a professional destruction service.

• Bic Camera (stores nationwide)
• PC Comfull (stores: Akihabara, Namba, Nagoya, Umeda, Kobe Sannomiya)
• Akihabara Final Disposal Site

It is unclear if all Bic Camera stores offer this service, so check in advance if necessary.

There have been reports on X and YouTube of data being found on storage devices purchased from second-hand shops.

Sometimes, users did not delete their data before selling, and sometimes data was recovered using recovery software.

In some videos, photos of the previous owner (with mosaic in the video) were actually found, so selling storage devices to second-hand shops without proper handling is risky.

How to Recover Data from Storage Devices (SSD/HDD)

This section explains how to recover data from storage devices.

First, let’s look at a comparison table of these two methods.

How to Use Recovery Tools

Using recovery tools can handle logical failures such as accidental data deletion, accidental drive formatting, and virus infections.

The cost is only several thousand yen, up to about 20,000 yen for the tool, and some tools allow free scanning with a trial version, so it is possible to check if recovery is possible before purchasing.

The recovery process is done by the user, but recovery tools are intuitive and very easy to use.

After scanning the specified storage device, the tool displays a list of recoverable data, and the user simply selects which files to recover.

The recovery time depends on the number of files, but it usually takes from several minutes to a day.

If there are only one or two files and the user is familiar with the process, recovery can be done in about five minutes.

The success rate is high if the data has not been overwritten, but it is not always 100%.

Even if the user does not overwrite the data, the system may do so by chance, or some other issue may prevent recovery.

The range of issues that can be handled is limited to logical failures, but the cost performance is high because it can be tried at low cost.

Therefore, unless there is obvious physical damage to the storage device, it is best to try this method first.

There is a review of recovery tools on another blog, so please refer to it.

≫ Related Article: [Pasolog] In-Depth Review of the Recovery Software ‘Recoverit’! A Strong Ally When Data is Accidentally Deleted

How to Request a Professional Service

Requesting a professional service is suitable when there is physical damage to the storage device or when it is difficult to recover data from a logical failure by oneself.

The cost depends on whether it is a physical or logical failure, the amount of data, and the extent of the damage, but it is much higher than recovery tools, ranging from tens of thousands to hundreds of thousands of yen.

Since professionals with specialized knowledge use special equipment for recovery, the cost is inevitably high.

Therefore, this option is considered when the data is irreplaceable, such as precious photos or videos, or important company documents, and is worth the high cost.

Although the recovery work is done by the professional, the user must remove the storage device from the computer and send it to the service provider.

Some providers may allow sending the entire computer, so check with each provider for details.

Summary: If You Respond Calmly, There Is Still a Chance to Recover Data

This article explained the basics of data recovery along with the mechanism of data deletion on storage devices.

Here is a summary of the key points:

There are two main ways to recover data: using software or requesting a professional service.

The range of issues that can be handled, costs, effort, and time required are all very different, so choose the method that suits your needs.

If data is lost, it is important to stop using the storage device immediately and be careful not to overwrite the data.

Also, if there is physical damage, requesting a professional service increases the chances of recovering the data.

In either case, compare the value of the data you want to recover with the cost, and choose the appropriate method.

This article also covers basic knowledge about storage standards and popular storage configurations, as well as how to choose storage from the perspectives of performance and compatibility.

≫ Related Article: How to Choose Storage (SSD/HDD) for Custom PCs [Performance / Features / Compatibility]

あわせて読みたい

PC Parts Estimation & Compatibility Check Tool

Automatically checks each component you need when selecting parts for a custom-built PC—perfect for beginners.